"That's the handwriting of a woman—a jealous woman," remarked Kennedy, handing to me a dainty note on plain paper which had come in the morning mail.

I did not stop to study the writing, for the contents of the
letter were more fascinating than even Kennedy's new science
of graphology.

You don't know me [the note read], but I know of your work
of scientific investigation.

Let me inform you of something that ought to interest you.

In the Forum Apartments you will find that there is some strange disease affecting the Wardlaw family. It is a queer disease of the nerves. One is dead. Others are dying.

Look into it.

A FRIEND.

As I read it I asked myself vainly what it could mean. There was no direct accusation against any one, yet the implication was plain. A woman had been moved by one of the primal passions to betray—some one.

I looked up from the note on the table at Craig. He was still studying the handwriting.

"It's that peculiar vertical, angular hand affected by many women," he commented, half to himself. "Even at a glance you can see that it's written hastily, as if under the stress of excitement and sudden resolution. You'll notice how those capitals—" The laboratory door opened, interrupting him.

"Hello, Kennedy," greeted Doctor Leslie, our friend, the coroner's physician, who had recently been appointed Health Commissioner of the city.

It was the first time we had seen him since the appointment and we hastened to congratulate him. He thanked us absently, and it was evident that there was something on his mind, some problem which, in his new office, he felt that he must solve if for no other purpose than to justify his reputation. Craig said nothing, preferring to let the commissioner come to the point in his own way.

"Do you know, Kennedy," he said, at length, turning in his chair and facing us, "I believe we have found one of the strangest cases in the history of the department."

The commissioner paused, then went on, quickly, "It looks as if it were nothing less than an epidemic of beriberi—not on a ship coming into port as so often happens, but actually in the heart of the city."

"Beriberi—in New York?" queried Craig, incredulously.

"It looks like it," reiterated Leslie, "in the family of a Doctor
Wardlaw, up-town here, in the Forum—"

Kennedy had already shoved over the letter he had just received. Leslie did not finish the sentence, but read the note in amazement.

"What are the symptoms?" inquired Craig.

"What makes you think it is beriberi, of all things?"

"Because they show the symptoms of beriberi," persisted Leslie, doggedly. "You know what they are like. If you care to go into the matter I think I can convince you."

The commissioner was still holding the letter and gazing, puzzled, from it to us. It seemed as if he regarded it merely as confirming his own suspicions that something was wrong, even though it shed no real light on the matter.

"How did you first hear of it?" prompted Kennedy.

Leslie answered frankly. "It came to the attention of the department as the result of a reform I have inaugurated. When I went in office I found that many of the death certificates were faulty, and in the course of our investigations we ran across one that seemed to be most vaguely worded. I don't know yet whether it was ignorance—or something worse. But it started an inquiry. I can't say that I'm thoroughly satisfied with the amended certificate of the physician who attended Mrs. Marbury, the mother of Doctor Wardlaw's wife, who died about a week ago—Doctor Aitken."

"Then Wardlaw didn't attend her himself?" asked Kennedy.

"Oh no. He couldn't, under the circumstances, as I'll show you presently, aside from the medical ethics of the case. Aitken was the family physician of the Marburys."

Kennedy glanced at the note. "One is dead. Others are dying," he read.
"Who are the others? Who else is stricken?"

"Why," continued Leslie, eager to unburden his story, "Wardlaw himself has the marks of a nervous affection as plainly as the eye can see it. You know what it is in this disease, as though the nerves were wasting away. But he doesn't seem half as badly affected as his wife. They tell me Maude Marbury was quite a beauty once, and photographs I have seen prove it. She's a wreck now. And, of course, the old lady must have been the most seriously affected of them all."

"Who else is there in the household?" inquired Kennedy, growing more and more interested.

"Well," answered Leslie, slowly, "they've had a nurse for some time,
Natalie Langdale. Apparently she has escaped."

"Any servants?"

"Some by the day; only one regularly—a Japanese, Kato. He goes home at night, too. There's no evidence of the disease having affected him."

I caught Leslie's eye as he gave the last information. Though I did not know much about beriberi, I had read of it, and knew that it was especially prevalent in the Orient. I did not know what importance to attach to Kato and his going home at night.

"Have you done any investigating yourself?" asked Kennedy.

Leslie hesitated a moment, as though deprecating his own efforts in that line, though when he spoke I could see no reason why he should, except that it had so often happened that Kennedy had seen the obvious which was hidden from most of those who consulted him.

"Yes," he replied, "I thought perhaps there might be some motive back of it all which I might discover. Possibly it was old Mrs. Marbury's fortune—not a large one, but substantial. So it occurred to me that the will might show it. I have been to the surrogate."

"And?" prompted Kennedy, approvingly.

"Mrs. Marbury's will has already been offered for probate. It directs, among other things, that twenty-five thousand dollars be given by her daughter, to whom she leaves the bulk of her fortune, to Doctor Aitken, who had been Mr. Marbury's physician and her own."

Leslie looked at us significantly, but Kennedy made no comment.

"Would you like to go up there and see them?" urged the commissioner, anxious to get Craig's final word on whether he would co-operate in the affair.

"I certainly should," returned Kennedy, heartily, folding up the letter which had first attracted his interest. "It looks as if there were more to this thing than a mere disease, however unusual."

Doctor Leslie could not conceal his satisfaction, and without delaying a moment more than was necessary hurried us out into one of the department cars, which he had left waiting outside, and directed the driver to take us to the Forum Apartments, one of the newest and most fashionable on the Drive.

Miss Langdale met us at the door and admitted us into the apartment. She was a striking type of trained nurse, one of those who seem bubbling over with health and vivacity. She seemed solicitous of her patients and reluctant to have them disturbed, yet apparently not daring to refuse to admit Doctor Leslie. There was nothing in her solicitude, however, that one could take exception to.

Miss Langdale conducted us softly down a hallway through the middle of the apartment, and I noted quickly how it was laid out. On one side we passed a handsomely furnished parlor and dining-room, opposite which were the kitchen and butler's pantry, and, farther along, a bedroom and the bath. On down the hall, on the right, was Doctor Wardlaw's study, or rather den, for it was more of a library than an office.

The nurse led the way, and we entered. Through the windows one caught a beautiful vista of the Drive, the river, and the Jersey shore. I gazed about curiously. Around the room there were bookcases and cabinets, a desk, some easy-chairs, and in the corner a table on which were some of Wardlaw's paraphernalia, for, although he was not a practising physician, he still specialized in his favorite branches of eye and ear surgery.

Miss Langdale left us a moment, with a hasty excuse that she must prepare Mrs. Wardlaw for the unexpected visit. The preparation, however, did not take long, for a moment later Maude Wardlaw entered, supported by her nurse.

Her lips moved mechanically as she saw us, but we could not hear what she said. As she walked, I could see that she had a peculiar gait, as though she were always lifting her feet over small obstacles. Her eyes, too, as she looked at us, had a strange squint, and now and then the muscles of her face twitched. She glanced from Leslie to Kennedy inquiringly, as Leslie introduced us, implying that we were from his office, then dropped into the easy-chair. Her breathing seemed to be labored and her heart action feeble, as the nurse propped her up comfortably.

As Mrs. Wardlaw's hand rested on the arm of the chair I saw that there was a peculiar flexion of her wrist which reminded me of the so-called "wrist-drop" of which I had heard. It was almost as if the muscles of her hands and arms, feet and legs, were weak and wasting. Once she had been beautiful, and even now, although she seemed to be a wreck of her former self, she had a sort of ethereal beauty that was very touching.

"Doctor is out—just now," she hesitated, in a tone that hinted at the loss of her voice. She turned appealingly to Miss Langdale. "Oh," she murmured, "I feel so badly this morning—as if pins and needles were sticking in me—vague pains in all my limbs—"

Her voice sank to a whisper and only her lips moved feebly. One had only to see her to feel sympathy. It seemed almost cruel to intrude under the circumstances, yet it was absolutely necessary if Craig were to accomplish anything. Maude Wardlaw, however, did not seem to comprehend the significance of our presence, and I wondered how Kennedy would proceed.

"I should like to see your Japanese servant, Kato," he began, directly, somewhat to my surprise, addressing himself rather to Miss Langdale than to Mrs. Wardlaw.

The nurse nodded and left the room without a word, as though appreciating the anomalous position in which she was placed as temporary mistress of the household.

A few moments later Kato entered. He was a typical specimen of the suave Oriental, and I eyed him keenly, for to me East was East and West was West, and I was frankly suspicious, especially as I saw no reason to be otherwise in Kennedy's manner. I waited eagerly to see what Craig would do.

"Sit here," directed Kennedy, indicating a straight-backed chair, on which the Japanese obediently sat. "Now cross your knees."

As Kato complied, Kennedy quickly brought his hand, held flat and palm upward, sharply against the Jap's knee just below the kneecap. There was a quick reflex jerk of the leg below the knee in response.

"Quite natural," Kennedy whispered, turning to Leslie, who nodded.

He dismissed Kato without further questioning, having had an opportunity to observe whether he showed any of the symptoms that had appeared in the rest of the family. Craig and the Health Commissioner exchanged a few words under their breath, then Craig crossed the room to Mrs. Wardlaw. The entrance of Kato had roused her momentarily and she had been watching what was going on.

"It is a simple test," explained Kennedy, indicating to Miss Langdale that he wished to repeat it on her patient.

Mrs. Wardlaw's knee showed no reflex! As he turned to us, we could see that Kennedy's face was lined deeply with thought, and he paced up and down the room once or twice, considering what he had observed.

I could see that even this simple interview had greatly fatigued Mrs. Wardlaw. Miss Langdale said nothing, but it was plainly evident that she objected strongly to the strain on her patient's strength.

"That will be sufficient," nodded Craig, noticing the nurse. "Thank you very much. I think you had better let Mrs. Wardlaw rest in her own room."

On the nurse's arm Mrs. Wardlaw withdrew and I looked inquiringly from Kennedy to Doctor Leslie. What was it that had made this beautiful woman such a wreck? It seemed almost as though the hand of fate had stretched out against one who had all to make her happy—wealth, youth, a beautiful home—for the sullen purpose of taking away what had been bestowed so bounteously.

"It is polyneuritis, all right, Leslie," Craig agreed, the moment we were alone.

"I think so," coincided Leslie, with a nod. "It's the CAUSE I can't get at. Is it polyneuritis of beriberi—or something else?" Kennedy did not reply immediately.

"Then there are other causes?" I inquired of Leslie.

"Alcohol," he returned, briefly. "I don't think that figures in this instance. At least I've seen no evidence."

"Perhaps some drug?" I hazarded at a venture.

Leslie shrugged.

"How about the food?" inquired Craig. "Have you made any attempt to examine it?"

"I have," replied the commissioner. "When I came up here first I thought of that. I took samples of all the food that I could find in the ice-box, the kitchen, and the butler's pantry. I have the whole thing, labeled, and I have already started to test them out. I'll show you what I have done when we go down to the department laboratory."

Kennedy had been examining the books in the bookcase and now pulled out a medical dictionary. It opened readily to the heading, "Polyneuritis—multiple neuritis."

I bent over and read with him. In the disease, it seemed, the nerve fibers themselves in the small nerves broke down and the affection was motor, sensory, vasomotor, or endemic. All the symptoms described seemed to fit what I had observed in Mrs. Wardlaw.

"Invariably," the article went on, "it is the result of some toxic substance circulating in the blood. There is a polyneuritis psychosis, known as Korsakoff's syndrome, characterized by disturbances of the memory of recent events and false reminiscences, the patient being restless and disorientated."

I ran my finger down the page until I came to the causes. There were alcohol, lead, arsenic, bisulphide of carbon, diseases such as diabetes, diphtheria, typhoid, and finally, much to my excitement, was enumerated beriberi, with the added information, "or, as the Japanese call it, kakke."

I placed my finger on the passage and was about to say something about my suspicions of Kato when we heard the sound of footsteps in the hall, and Craig snapped the book shut, returning it hastily to the bookcase. It was Miss Langdale who had made her patient comfortable in bed and now returned to us.

"Who is this Kato?" inquired Craig, voicing what was in my own mind.
"What do you know about him?"

"Just a young Japanese from the Mission downtown," replied the nurse, directly. "I don't suppose you know, but Mrs. Wardlaw used to be greatly interested in religious and social work among the Japanese and Chinese; would be yet, but," she added, significantly, "she is not strong enough. They employed him before I came here, about a year ago, I think."

Kennedy nodded, and was about to ask another question, when there was a slight noise out in the hall. Thinking it might be Kato himself, I sprang to the door.

Instead, I encountered a middle-aged man, who drew back in surprise at seeing me, a stranger.

"Oh, good morning, Doctor Aitken!" greeted Miss Langdale, in quite the casual manner of a nurse accustomed to the daily visit at about this hour.

As for Doctor Aitken, he glanced from Leslie, whom he knew, to Kennedy, whom he did not know, with a very surprised look on his face. In fact, I got the impression that after he had been admitted he had paused a moment in the hall to listen to the strange voices in the Wardlaw study.

Leslie nodded to him and introduced us, without quite knowing what to say or do, any more than Doctor Aitken.

"A most incomprehensible case," ventured Aitken to us. "I can't, for the life of me, make it out." The doctor showed his perplexity plainly, whether it was feigned or not.

"I'm afraid she's not quite so well as usual," put in Miss Langdale, speaking to him, but in a manner that indicated that first of all she wished any blame for her patient's condition to attach to us and not to herself.

Doctor Aitken pursed up his lips, bowed excusingly to us, and turned down the hall, followed by the nurse. As they passed on to Mrs. Wardlaw's room, I am sure they whispered about us. I was puzzled by Doctor Aitken. He seemed to be sincere, yet, under the circumstances, I felt that I must be suspicious of everybody and everything.

Alone again for a moment, Kennedy turned his attention to the furniture of the room, and finally paused before a writing-desk in the corner. He tried it. It was not locked and he opened it. Quickly he ran through a pile of papers carefully laid under a paper-weight at the back.

A suppressed exclamation from him called my attention to something that he had discovered. There lay two documents, evidently recently drawn up. As we looked over the first, we saw that it was Doctor Wardlaw's will, in which he had left everything to his wife, although he was not an especially wealthy man. The other was the will of Mrs. Wardlaw.

We devoured it hastily. In substance it was identical with the first, except that at the end she had added two clauses. In the first she had done just as her mother had directed. Twenty-five thousand dollars had been left to Doctor Aitken. I glanced at Kennedy, but he was reading on, taking the second clause. I read also. Fifty thousand dollars was given to endow the New York Japanese Mission.

Immediately the thought of Kato and what Miss Langdale had just told us flashed through my mind.

A second time we heard the nurse's footsteps on the hardwood floor of the hall. Craig closed the desk softly.

"Doctor Aitken is ready to go," she announced. "Is there anything more you wish to ask?"

Kennedy spoke a moment with the doctor as he passed out, but, aside from the information that Mrs. Wardlaw was, in his opinion, growing worse, the conversation added nothing to our meager store of information.

"I suppose you attended Mrs. Marbury?" ventured Kennedy of Miss
Langdale, after the doctor had gone.

"Not all the time," she admitted. "Before I came there was another nurse, a Miss Hackstaff."

"What was the matter? Wasn't she competent?"

Miss Langdale avoided the question, as though it were a breach of professional etiquette to cast reflections on another nurse, although whether that was the real reason for her reticence did not appear. Craig seemed to make a mental note of the fact.

"Have you seen anything—er—suspicious about this Kato?" put in
Leslie, while Kennedy frowned at the interruption.

Miss Langdale answered quickly, "Nothing."

"Doctor Aitken has never expressed any suspicion?" pursued Leslie.

"Oh no," she returned. "I think I would have known it if he had any. No, I've never heard him even hint at anything." It was evident that she wished us to know that she was in the confidence of the doctor.

"I think we'd better be going," interrupted Kennedy, hastily, not apparently pleased to have Leslie break in in the investigation just at present.

Miss Langdale accompanied us to the door, but before we reached it it was opened from the outside by a man who had once been and yet was handsome, although one could see that he had a certain appearance of having neglected himself.

Leslie nodded and introduced us. It was Doctor Wardlaw.

As I studied his face I could see that, as Leslie had already told us, it plainly bore the stigma of nervousness.

"Has Doctor Aitken been here?" he inquired, quickly, of the nurse.
Then, scarcely waiting for her even to nod, he added: "What did he say?
Is Mrs. Wardlaw any better?"

Miss Langdale seemed to be endeavoring to make as optimistic a report as the truth permitted, but I fancied Wardlaw read between the lines. As they talked it was evident that there was a sort of restraint between them. I wondered whether Wardlaw might not have some lurking suspicion against Aitken, or some one else. If he had, even in his nervousness he did not betray it.

"I can't tell you how worried I am," he murmured, almost to himself.
"What can this thing be?"

He turned to us, and, although he had just been introduced, I am sure that our presence seemed to surprise him, for he went on talking to himself, "Oh yes—let me see—oh yes, friends of Doctor—er—Leslie."

I had been studying him and trying to recall what I had just read of beriberi and polyneuritis. There flashed over my mind the recollection of what had been called Korsakoff's syndrome, in which one of the mental disturbances was the memory of recent events. Did not this, I asked myself, indicate plainly enough that Leslie might be right in his suspicions of beriberi? It was all the more apparent a moment later when, turning to Miss Langdale, Wardlaw seemed almost instantly to forget our presence again. At any rate, his anxiety was easy to see.

After a few minutes' chat during which Craig observed Wardlaw's symptoms, too, we excused ourselves, and the Health Commissioner undertook to conduct us to his office to show us what he had done so far. As for me, I could not get Miss Langdale out of my mind, and especially the mysterious letter to Kennedy. What of it and what of its secret sender?

None of us said much until, half an hour later, in the department laboratory, Leslie began to recapitulate what he had already done in the case.

"You asked whether I had examined the food," he remarked, pausing in a corner before several cages in which were a number of pigeons, separated and carefully tagged. With a wave of his hand at one group of cages he continued: "These fellows I have been feeding exclusively on samples of the various foods which I took from the Wardlaw family when I first went up there. Here, too, are charts showing what I have observed up to date. Over there are the 'controls'—pigeons from the same group which have been fed regularly on the usual diet so that I can check my tests."

Kennedy fell to examining the pigeons carefully as well as the charts and records of feeding and results. None of the birds fed on what had been taken from the apartment looked well, though some were worse than others.

"I want you to observe this fellow," pointed out Leslie at last, singling out one cage. The pigeon in it was a pathetic figure. His eyes seemed dull and glazed. He paid little or no attention to us; even his food and water did not seem to interest him. Instead of strutting about, he seemed to be positively wabbly on his feet. Kennedy examined this one longer and more carefully than any of the rest.

"There are certainly all the symptoms of beriberi, or rather, polyneuritis, in pigeons, with that bird," admitted Craig, finally, looking up at Leslie.

The commissioner seemed to be gratified. "You know," he remarked, "beriberi itself is a common disease in the Orient. There has been a good deal of study of it and the cause is now known to be the lack of something in the food, which in the Orient is mostly rice. Polishing the rice, which removes part of the outer coat, also takes away something that is necessary for life, which scientists now call 'vitamines.'"

"I may take some of these samples to study myself?" interrupted
Kennedy, as though the story of vitamines was an old one to him.

"By all means," agreed Leslie.

Craig selected what he wanted, keeping each separate and marked, and excused himself, saying that he had some investigations of his own that he wished to make and would let Leslie know the result as soon as he discovered anything.

Kennedy did not go back directly to the laboratory, however. Instead, he went up-town and, to my surprise, stopped at one of the large breweries. What it was that he was after I could not imagine, but, after a conference with the manager, he obtained several quarts of brewer's yeast, which he had sent directly down to the laboratory.

Impatient though I was at this seeming neglect of the principal figures in the case, I knew, nevertheless, that Kennedy had already schemed out his campaign and that whatever it was he had in mind was of first importance.

Back at last in his own laboratory, Craig set to work on the brewer's yeast, deriving something from it by the plentiful use of a liquid labeled "Lloyd's reagent," a solution of hydrous aluminum silicate.

After working for some time, I saw that he had obtained a solid which he pressed into the form of little whitish tablets. He had by no means finished, but, noticing my impatience, he placed the three or four tablets in a little box and handed them to me.

"You might take these over to Leslie in the department laboratory, Walter," he directed. "Tell him to feed them to that wabbly-looking pigeon over there—and let me know the moment he observes any effect."

Glad of the chance to occupy myself, I hastened on the errand, and even presided over the first feeding of the bird.

When I returned I found that Kennedy had finished his work with the brewer's yeast and was now devoting himself to the study of the various samples of food which he had obtained from Leslie.

He was just finishing a test of the baking-powder when I entered, and his face showed plainly that he was puzzled by something that he had discovered.

"What is it?" I asked. "Have you found out anything?"

"This seems to be almost plain sodium carbonate," he replied, mechanically.

"And that indicates?" I prompted.

"Perhaps nothing, in itself," he went on, less abstractedly. "But the use of sodium carbonate and other things which I have discovered in other samples disengages carbon dioxide at the temperature of baking and cooking. If you'll look in that public-health report on my desk you'll see how the latest investigations have shown that bicarbonate of soda and a whole list of other things which liberate carbon dioxide destroy the vitamines Leslie was talking about. In other words, taken altogether I should almost say there was evidence that a concerted effort was being made to affect the food—a result analogous to that of using polished rice as a staple diet—and producing beriberi, or, perhaps more accurately, polyneuritis. I can be sure of nothing yet, but—it's worth following up."

"Then you think Kato—"

"Not too fast," cautioned Craig. "Remember, others had access to the kitchen, too."

In spite of his hesitancy, I could think only of the two paragraphs we had read in Mrs. Wardlaw's will, and especially of the last. Might not Kato have been forced or enticed into a scheme that promised a safe return and practically no chance of discovery? What gruesome mystery had been unveiled by the anonymous letter which had first excited our curiosity?

It was late in the afternoon that Commissioner Leslie called us up, much excited, to inform us that the drooping pigeon was already pecking at food and beginning to show some interest in life. Kennedy seemed greatly gratified as he hung up the receiver.

"Almost dinner-time," he commented, with a glance at his watch. "I think we'll make another hurried visit to the Wardlaw apartment."

We had no trouble getting in, although as outsiders we were more tolerated than welcome. Our excuse was that Kennedy had some more questions which we wished to ask Miss Langdale.

While we waited for her we sat, not in the study, but in the parlor. The folding-doors into the dining-room were closed, but across the hall we could tell by the sound when Kato was in the kitchen and when he crossed the hall.

Once I heard him in the dining-room. Before I knew it Kennedy had hastily tiptoed across the hall and into the kitchen. He was gone only a couple of minutes, but it was long enough to place in the food that was being prepared, and in some unprepared, either the tablets he had made or a powder he had derived from them crushed up. When he returned I saw from his manner that the real purpose of the visit had been accomplished, although when Miss Langdale appeared he went through the form of questioning her, mostly on Mrs. Marbury's sickness and death. He did not learn anything that appeared to be important, but at least he covered up the reason for his visit. Outside the apartment, Kennedy paused a moment. "There's nothing to do now but await developments," he meditated. "Meanwhile, there is no use for us to double up our time together. I have decided to watch Kato to-night. Suppose you shadow Doctor Aitken. Perhaps we may get a line on something that way."

The plan seemed admirable to me. In fact, I had been longing for some action of the sort all the afternoon, while Kennedy had been engaged in the studies which he evidently deemed more important.

Accordingly, after dinner, we separated, Kennedy going back to the
Forum Apartments to wait until Kato left for the night, while I walked
farther up the Drive to the address given in the directory as that of
Doctor Aitken.

It happened to be the time when the doctor had his office hours for patients, so that I was sure at least that he was at home when I took my station just down the street, carefully scrutinizing every one who entered and left his house.

Nothing happened, however, until the end of the hour during which he received office calls. As I glanced down the street I was glad that I had taken an inconspicuous post, for I could see Miss Langdale approaching. She was not in her nurse's uniform, but seemed to be off duty for an hour or two, and I must confess she was a striking figure, even in that neighborhood which was noted for its pretty and daintily gowned girls. Almost before I knew it she had entered the English-basement entrance of Doctor Aitken's.

I thought rapidly. What could be the purpose of her visit? Above all, how was I, on the outside, to find out? I walked down past the house. But that did no good. In a quandary, I stopped. Hesitation would get me nothing. Suddenly an idea flashed through my mind. I turned in and rang the bell.

"It's past the doctor's office hours," informed a servant who opened the door. "He sees no one after hours."

"But," I lied, "I have an appointment. Don't disturb him. I can wait."

The waiting-room was empty, I had seen, and I was determined to get in at any cost. Reluctantly the servant admitted me.

For several moments I sat quietly alone, fearful that the doctor might open the double doors of his office and discover me. But nothing happened and I grew bolder. Carefully I tiptoed to the door. It was of solid oak and practically impervious to sound. The doors fitted closely, too. Still, by applying my ear, I could make out the sound of voices on the other side. I strained my ears both to catch a word now and then and to be sure that I might hear the approach of anybody outside.

Was Aitken suspiciously interested in the pretty nurse—or was she suspiciously interested in him?

Suddenly their voices became a trifle more distinct. "Then you think Doctor Wardlaw has it, too?" I heard her ask. I did not catch the exact reply, but it was in the affirmative.

They were approaching the door. In a moment it would be opened. I waited to hear no more, but seized my hat and dashed for the entrance from the street just in time to escape observation. Miss Langdale came out shortly, the doctor accompanying her to the door, and I followed her back to the Forum.

What I had heard only added to the puzzle. Why her anxiety to know whether Wardlaw himself was affected? Why Aitken's solicitude in asserting that he was? Were they working together, or were they really opposed? Which might be using the other?

My queries still unanswered, I returned to Aitken's and waited about some time, but nothing happened, and finally I went on to our own apartment.

It was very late when Craig came in, but I was still awake and waiting for him. Before I could ask him a question he was drawing from me what I had observed, listening attentively. Evidently he considered it of great importance, though no remark of his betrayed what interpretation he put on the episode.

"Have you found anything?" I managed to ask, finally.

"Yes, indeed," he nodded, thoughtfully. "I shadowed Kato from the
Forum. It must have been before Miss Langdale came out that he left. He
lives down-town in a tenement-house. There's something queer about that
Jap."

"I think there is," I agreed. "I don't like his looks."

"But it wasn't he who interested me so much to-night," Craig went on, ignoring my remark, "as a woman."

"A woman?" I queried, in surprise. "A Jap, too?"

"No, a white woman, rather good-looking, too, with dark hair and eyes. She seemed to be waiting for him. Afterward I made inquiries. She has been seen about there before."

"Who was she?" I asked, fancying perhaps Miss Langdale had made another visit while she was out, although from the time it did not seem possible.

"I followed her to her house. Her name is Hackstaff—"

"The first trained nurse!" I exclaimed.

"Miss Hackstaff is an enigma," confessed Kennedy. "At first I thought that perhaps she might be one of those women whom the Oriental type fascinated, that she and Kato might be plotting. Then I have considered that perhaps her visits to Kato may be merely to get information—that she may have an ax to grind. Both Kato and she will bear watching, and I have made arrangements to have it done. I've called on that young detective, Chase, whom I've often used for the routine work of shadowing. There's nothing more that we can do now until to-morrow, so we might as well turn in."

Early the next day Kennedy was again at work, both in his own laboratory and in that of the Health Department, making further studies of the food and the effect it had on the pigeons, as well as observing what changes were produced by the white tablets he had extracted from the yeast.

It was early in the forenoon when the buzzer on the laboratory door sounded and I opened the door to admit Chase in a high state of excitement.

"What has happened?" asked Craig, eagerly.

"Many things," reported the young detective, breathlessly. "To begin with, I followed Miss Hackstaff from her apartment this morning. She seemed to be worked up over something—perhaps had had a sleepless night. As nearly as I could make out she was going about aimlessly. Finally, however, I found that she was getting into the neighborhood of Doctor Aitken and of the Forum. Well, when we got to the Forum she stopped and waited in front of it—oh, I should say almost half an hour. I couldn't make out what it was she wanted, but at last I found out."

He paused a moment, then raced on, without urging. "Miss Langdale came out—and you should have seen the Hackstaff woman go for her." He drew in his breath sharply at the reminiscence. "I thought there was going to be a murder done—on Riverside Drive. Miss Langdale screamed and ran back into the apartment. There was a good deal of confusion. The hall-boys came to the rescue. In the excitement, I managed to slip into the elevator with her. No one seemed to think it strange then that an outsider should be interested. I went up with her—saw Wardlaw, as she poured out the story. He's a queer one. Is he RIGHT?"

"Why?" asked Craig, indulgently.

"He seems so nervous; things upset him so easily. Yet, after we had taken care of Miss Langdale and matters had quieted down, I thought I might get some idea of the cause of the fracas and asked him if he knew of any reason. Why, he looked at me kind of blankly, and I swear he acted as though he had almost forgotten it already. I tell you, he's not RIGHT."

Remembering our own experience, I glanced significantly at Craig. "Korsakoff's syndrome?" I queried, laconically. "Another example of a mind confused even on recent events?"

Kennedy, however, was more interested in Chase. "What did Miss
Hackstaff do?" he asked.

"I don't know. I missed her. When I got out again she was gone."

"Pick her up again," directed Craig. "Perhaps you'll get her at her place. And see, this time, if you can get what I asked you."

"I'll try," returned Chase, much pleased at the words of commendation which Craig added as he left us again.

On what errand Chase had gone I could not guess, except that it had something to do with this strange woman who had so unexpectedly entered the case. Nor was Craig any more communicative. There were evidently many problems which only events could clear up even in his mind. Though he did not say anything, I knew that he was as impatient as I was, and as Leslie, too, who called up once or twice to learn whether he had discovered anything. There was nothing to do but wait.

It was early in the afternoon that the telephone rang and I answered it. It was Chase calling Kennedy. I heard only half the conversation and there was not much of that, but I knew that something was about to happen. Craig hastily summoned a cab, then in rapid succession called up Doctor Aitken and Leslie, for whom we stopped as our driver shot us over to the Forum Apartments.

There was no ceremony or unnecessary explanation about our presence, as Kennedy entered and directed Miss Langdale to bring her patients into the little office-study of Doctor Wardlaw.

Miss Langdale obeyed reluctantly. When she returned I felt that it was appreciable that a change had taken place. Mrs. Wardlaw, at least, was improved. She was still ill, but she seemed to take a more lively interest in what was going on about her. As for Doctor Wardlaw, however, I could not see that there had been any improvement in him. His nervousness had not abated. Kato, whom Kennedy summoned at the same time, preserved his usual imperturbable exterior. Miss Langdale, in spite of the incident of the morning, was quite as solicitous as ever of her charges.

We had not long to wait for Doctor Aitken. He arrived, inquiring anxiously what had happened, although Kennedy gave none of us any satisfaction immediately as to the cause of his quick action. Aitken fidgeted uneasily, glancing from Kennedy to Leslie, then to Miss Langdale, and back to Kennedy, without reading any explanation in the faces. I knew that Craig was secretly taking his time both for its effect on those present and to give Chase a chance.

"Our poisons and our drugs," he began, leisurely, at length, "are in many instances the close relatives of harmless compounds that represent the intermediate steps in the daily process of metabolism. There is much that I might say about protein poisons. However, that is not exactly what I want to talk about—at least first."

He stopped to make sure that he had the attention of us all. As a matter of fact, his manner was such that he attracted even the vagrant interest of the Wardlaws.

"I do not know how much of his suspicions Commissioner Leslie has communicated to you," he resumed, "but I believe that you have all heard of the disease beriberi so common in the Far East and known to the Japanese as kakke. It is a form of polyneuritis and, as you doubtless know, is now known to be caused, at least in the Orient, by the removal of the pericarp in the polishing of rice. Our milling of flour is, in a minor degree, analogous. To be brief, the disease arises from the lack in diet of certain substances or bodies which modern scientists call vitamines. Small quantities of these vital principles are absolutely essential to normal growth and health and even to life itself. They are nitrogenous compounds and their absence gives rise to a class of serious disorders in which the muscles surrender their store of nitrogen first. The nerves seems to be the preferred creditors, so to speak. They are affected only after the muscles begin to waste. It is an abstruse subject and it is not necessary for me to go deeper into it now."

I controlled my own interest in order to watch those about me. Kato, for one, was listening attentively, I saw.

"In my studies of the diet of this household," continued Kennedy, "I have found that substances have been used in preparing food which kill vitamines. In short, the food has been denatured. Valuable elements, necessary elements, have been taken away."

"I, sir, not always in kitchen, sir," interrupted Kato, still deferential. "I not always know—"

With a peremptory wave of his hand Kennedy silenced the Jap.

"It has long been a question," he hurried on, "whether these vitamines are tangible bodies or just special arrangements of molecules. Recently government investigators have discovered that they are bodies that can be isolated by a special process from the filtrate of brewer's yeast by Lloyd's reagent. Five grams of this"—he held up some of the tablets he had made—"for a sixty-kilogram person each day are sufficient. Unknown to you, I have introduced some of this substance into the food already deficient in vitamines. I fancy that even now I can detect a change," he nodded toward Mrs. Wardlaw.

There was a murmur of surprise in the room, but before Craig could continue further the door opened and Mrs. Wardlaw uttered a nervous exclamation. There stood Chase with a woman. I recognized her immediately from Kennedy's description as Miss Hackstaff.

Chase walked deliberately over to Kennedy and handed him something, while the nurse glanced calmly, almost with pity, at Mrs. Wardlaw, ignoring Wardlaw, then fixing her gaze venomously on Miss Langdale. Recalling the incident of the morning, I was ready to prevent, if necessary, a repetition now. Neither moved. But it was a thrilling, if silent, drama as the two women glared at each other.

Kennedy was hastily comparing the anonymous note he had received with something Chase had brought.

"Some one," he shot out, suddenly, looking up and facing us, "has, as I have intimated, been removing or destroying the vital principle in the food—these vitamines. Clearly the purpose was to make this case look like an epidemic of beriberi, polyneuritis. That part has been clear to me for some time. It has been the source of this devilish plot which has been obscure. Just a moment, Kato, I will do the talking. My detective, Chase, has been doing some shadowing for me, as well as some turning over of past history. He has found a woman, a nurse, more than a nurse, a secret lover, cast off in favor of another. Miss Hackstaff—you wrote that letter—it is your hand—for revenge—on Miss Langdale and—"

"You shan't have him!" almost hissed Helen Hackstaff. "If I cannot—no one shall!"

Natalie Langdale faced her, defiant. "You are a jealous, suspicious person," she cried. "Doctor Aitken knows—"

"One moment," interrupted Craig. "Mrs. Marbury is gone. Mrs. Wardlaw is weakened. Yet all who are affected with nerve troubles are not necessarily suffering from polyneuritis. Some one here has been dilettanting with death. It is of no use," he thundered, turning suddenly on a cowering figure. "You stood to win most, with the money and your unholy love. But Miss Hackstaff, cast off, has proved your Nemesis. Your nervousness is the nervousness not of polyneuritis, but of guilt, Doctor Wardlaw!"