He gave me no time for questions, and I had no ability to reconstruct my own theory of the case as we hustled into our clothes to catch the early morning train.

"Broadhurst is at the Idlewild Hotel," Kennedy said, as we left the apartment, "and I think we can make it quicker by railway than by motor."

The turfman met us at the station.

"Tell me just what happened," asked Kennedy.

"No one seems to understand just what it was," Broadhurst explained, "but, as nearly as I remember, Murchie was the lion of the Idlewild grillroom all the evening. He had 'come back.' Once, I recall, he was paged, and the boy told him someone was waiting outside. He went out, and returned, considerably flushed and excited.

"'By George,' he said, 'a man never raises his head above the crowd but that there's somebody there to take a crack at it! There must have been some crank outside, for before I could get a look in the dark, I was seized. I managed to get away. I got a little scratch with a knife or a pin, though,' he said, dabbing at a cut on his neck."

"What then?" prompted Kennedy.

"None of us paid much attention to it," resumed Broadhurst, "until just as another toast was proposed to Lady Lee and someone suggested that Murchie respond to it, we turned to find him huddled up in his chair, absolutely unconscious. The house physician could find nothing wrong apparently—in fact, said it was entirely a case of heart failure. I don't think any of us would question his opinion if it had not been for Murchie's peculiar actions when he came back to the room that time."

Murchie's body had been removed to the local undertaking establishment. As Broadhurst drove up there and we entered, Kennedy seemed interested only in the little jab and a sort of swelling upon the neck of the dead man. Quickly he made a little incision beside it, and about ten or a dozen drops of what looked like blood-serum oozed out on a piece of gauze which Craig held.

As we turned to leave the undertaker's, a striking, dark-haired girl, with the color gone from her cheeks, hurried past us and fell on her knees beside Murchie's body. It was the woman who had congratulated him the day before, the woman of the panel—AmÉlie Guernsey.

I had not noticed, up to this point, another woman who was standing apart in the crowd, but now I happened to catch her eye. It was the woman whose picture with the two children hung in Murchie's apartment. Kennedy drew me back into the crowd, and there we watched the strange tragedy of the wife that was and the wife that was to have been.

Craig hurried back to the city after that, and, as we pushed our way up the ramp from the station, he looked hastily at his watch.

"Walter," he said, "I want you to locate Cecilie Safford and let me know at the laboratory the moment you find her. And perhaps it would be well to start at the police station."

It seemed to me as though the girl whom we had found so easily the evening before had now utterly disappeared. At the police station she had not been held, but had given an address which had proved fictitious. At the cabaret saloon no one had seen her since the incident of the fight.

As I left the place, I ran into Donovan, of the Tenderloin squad, and put the case to him. He merely laughed.

"Of course I could find her any time I wanted to," he said. "I knew that was a fake address."

He gave me the real address, and I hurried to the nearest telephone to call up Craig.

"Have Donovan bring her over here as soon as he can find her," he called back.

When I arrived at the laboratory, I found Kennedy engrossed in his tests.

"Have you found anything definite?" I asked anxiously.

He nodded, but would say nothing.

"I've telephoned Broadhurst," he remarked, a moment later. "You remember that the former Mrs. Murchie was at Belmore Inn. I have asked him to stop and get her on the way down here in the car with McGee, and to get AmÉlie Guernsey at the Idlewild, too." He continued to work. "And, oh yes," he added: "I have asked Inspector O'Connor to take up another line, too."

It was a strange gathering that assembled that forenoon. Donovan arrived soon after I did, and with him, sure enough, was Cecilie Safford. A few moments later Broadhurst's car swung up to the door, and Broadhurst entered, accompanied by AmÉlie Guernsey. McGee followed, with the former Mrs. Murchie.

"I don't want another job like that," whispered Broadhurst to Kennedy. "I'm nearly frozen. Neither of those women has spoken a word since we started."

"You can hardly blame them," returned Kennedy.

Mrs. Murchie was still a handsome woman. She now carried herself with an air of assumed dignity. AmÉlie Guernsey had regained her color in the excitement of the ride and was, if anything, more beautiful than ever. But, as Broadhurst intimated, one could almost feel the frigidity of the atmosphere as the three women who had played such dramatic parts in Murchie's life sat there, trying to watch and, at the same time, avoid each other's gaze.

The suspense was relieved when O'Connor came in in a department car. With him were the young man who had been seated with Cecilie at the table the night of the fight and also the gunman.

"The magistrate in the night court settled the case that night," informed O'Connor, under his breath, laying down two slips of paper before Kennedy, "but I have their pedigrees. That fellow's name is Ronald Mawson," he said, pointing to Cecilie's companion, then indicating the gunman, "That's Frank Giani—Frank the Wop."

I watched Mawson and Cecilie closely, but could discover nothing. They scarcely looked at each other.

McGee, however, glared at both Mawson and the gunman, though none of them said a word.

"They used to be out there as stable-boys at Broadhurst's," I heard O'Connor continue, in a whisper. "I think they had a run-in and were fired. Each says the other got him in wrong."

A moment later Kennedy began:

"When you came to my laboratory the other day, Mr. Broadhurst," he said, "you remarked that perhaps this case might be a little out of my line, but that I might find it sufficiently interesting. I can assure you that I have not only found it interesting, but astounding. I have seldom had the privilege of unraveling a mystery which was so cleverly rigged and in which there are so many cross-currents of human passion."

"Then you think Lady Lee was doped?" asked Broadhurst.

"Doped?" interjected McGee quickly. "Why, Mr. Broadhurst, you remember what the veterinary said. He couldn't find any signs of heroin or any other dope they use."

"That's the devilish ingenuity of it all," shot out Kennedy suddenly, holding up a little beaker in which there was some colorless fluid. "I am merely going to show you now what can be done by the use of one of the latest discoveries of physiological chemistry."

He took a syringe and, drawing back the plunger, filled it with the liquid. With a slight jab of cocaine to make the little operation absolutely painless, he injected the fluid into the livelier of our two guinea-pigs.

"While you and Murchie were absent the first day that I went out to your stable, I succeeded in drawing off some of the blood of Lady Lee," Craig resumed, talking to Broadhurst. "Here, in my laboratory, I have studied it. Lady Lee, that day, had had no more than the ordinary amount of exercise, yet she was completely fagged."

By this time the little guinea-pig had become more and more listless and was now curled up in a corner sound asleep.

"I have had to work very hurriedly this morning," Craig continued, "but it has only been covering ground over which I have already gone. I was already studying a peculiar toxin. And from the fluid I obtained from Murchie's body, I have been able to calculate that a deadly dose of that same powerful poison killed him."

Kennedy plunged directly from this startling revelation into his proof.

"Perhaps you have heard of the famous German scientist, Weichardt, of Berlin," he resumed, "and his remarkable investigations into the toxin of fatigue. Scientists define fatigue as the more or less complete loss of the power of muscles to respond to stimulation due to their normal activity. An interval of rest is usually enough to bring about their return to some degree of power. But for complete return to normal condition, a long interval may be necessary.

"As the result of chemical changes which occur in a muscle from contraction, certain substances are formed which depress or inhibit the power of contraction. Extracts made from the fatigued muscles of one frog, for instance, when injected into the circulation of another frog bring on an appearance of fatigue in the latter. Extracts from unfatigued muscles give no such results. More than that, the production of this toxin of fatigue by the exercise of one set of muscles, such as those of the legs in walking, greatly diminishes the amount of work obtainable from other unused muscles, such as those of the arms."

Kennedy went on, looking at the sleeping guinea-pig rather than at us:

"Weichardt has isolated from fatigued muscles a true toxin of a chemical and physical nature, like the bacterial toxins, which, when introduced into the blood, gives rise to the phenomena of fatigue. This is the toxin of fatigue—kenotoxin. Those who have studied the subject have found at least three fatigue substances—free sarcolactic acid, carbon dioxide, and monopotassium phosphate, which is so powerful that, after the injection of one-fifteenth of a gram, the poisoned muscle shows signs of fatigue and is scarcely able to lift a weight easily lifted in normal conditions. Other fatigue products may be discovered; but, if present in large quantity or in small quantity for a long time, each of the substances I have named will cause depression or fatigue of muscles.

"Further than that," continued Kennedy, "the depressing influence of these substances on what is known as striated muscle—heart muscle—is well known. The physician at the Idlewild might very well have mistaken the cause of the relaxation of Murchie's heart. For German investigators have also found that the toxin of fatigue, when injected into the circulation of a fresh animal, may not only bring on fatigue but may even cause death—as it did finally here." Kennedy paused. "Lady Lee," he said, looking from one to the other of his audience keenly, "Lady Lee was the first victim of the fiendish cunning of this—"

A shrill voice interrupted.

"But Lady Lee won the race!"

It was McGee, the jockey. Kennedy looked at him a moment, then tapped another beaker on the table before him.

"Weichardt has also obtained, by the usual methods," he replied, "an antitoxin with the power of neutralizing the fatigue properties of the toxin. You thought Lady Lee was not friendly with strangers that morning at the track. She was not, when the stranger jabbed a needle into her neck and pumped an extra large dose of the antitoxin of fatigue into her just in time to neutralize, before the race, the long series of injections of fatigue toxin."

Kennedy was now traveling rapidly toward the point which he had in view. He drew from his pocket the little bottle which he had picked up that night in the cabaret saloon.

"One word more," he said, as he held up the bottle and faced Cecilie Safford, who was now trembling like a leaf ready to fall: "If one with shattered nerves were unable to sleep, can you imagine what would be a most ideal sedative—especially if to take almost any other drug would be merely to substitute that habit for another?"

He waited a moment, then answered his own question.

"Naturally," he proceeded, "it might be, theoretically at least, a small dose of those products of fatigue by which nature herself brings on sleep. I am not going into the theory of the thing. The fact that you had such a thing is all that interests me."

I watched the girl's eyes as they were riveted on Kennedy. She seemed to be fascinated, horrified.

"This bottle contains a weak solution of the toxin of fatigue," persisted Kennedy.

I thought she would break down, but, by a mighty effort, she kept her composure and said nothing.

"Someone was trying to discredit and ruin Murchie by making the horses he trained lose races—somebody whose life and happiness Murchie himself had already ruined.

"That person," pursued Kennedy relentlessly, "was defeated in the attempt to discredit Murchie when, by my injection of the antitoxin, Lady Lee finally did win. In that person's mind, Murchie, not the horse, had won.

"The wild excitement over Murchie's vindication drove that person to desperation. There was only one more road to revenge. It was to wait until Murchie himself could be easily overpowered, when an overwhelming dose of this fatigue toxin could be shot into him—the weapon that had failed on the horses turned on himself. Besides, no one—not even the most expert physician or chemist—would ever suspect that Murchie's death was not natural."

"That—that bottle is mine—mine!" shouted a wild voice interrupting. "I took it—I used it—I—"

"Just a moment, Miss Safford," entreated Kennedy. "That person," he rapped out sharply, picking up the pedigrees O'Connor had handed him, "that person gave the toxin to a poor dope fiend as a sleeping-potion in one strength, gave it to Lady Lee in still another strength, and to Murchie in its most fatal strength. It was the poor and unknown pharmacist described in this pedigree whose dream of happiness Murchie shattered when he captivated Cecilie Safford—her deserted lover, Ronald Mawson."