Edwards crumpled up as Kennedy and I faced him. There was no escape. In fact our greatest difficulty was to protect him from Waldon.

Kennedy's work in the case was over when we had got Edwards ashore and in the hands of the authorities. But mine had just begun and it was late when I got my story on the wire for the Star.

I felt pretty tired and determined to make up for it by sleeping the next day. It was no use, however.

"Why, what's the matter, Mrs. Northrop?" I heard Kennedy ask as he opened our door the next morning, just as I had finished dressing.

He had admitted a young woman, who greeted us with nervous, wide-staring eyes.

"It's—it's about Archer," she cried, sinking into the nearest chair and staring from one to the other of us.

She was the wife of Professor Archer Northrop, director of the archeological department at the university. Both Craig and I had known her ever since her marriage to Northrop, for she was one of the most attractive ladies in the younger set of the faculty, to which Craig naturally belonged. Archer had been of the class below us in the university. We had hazed him, and out of the mild hazing there had, strangely enough, grown a strong friendship.

I recollected quickly that Northrop, according to last reports, had been down in the south of Mexico on an archeological expedition. But before I could frame, even in my mind, the natural question in a form that would not alarm his wife further, Kennedy had it on his lips.

"No bad news from Mitla, I hope?" he asked gently, recalling one of the main working stations chosen by the expedition and the reported unsettled condition of the country about it. She looked up quickly.

"Didn't you know—he—came back from Vera Cruz yesterday?" she asked slowly, then added, speaking in a broken tone, "and—he seems—suddenly—to have disappeared. Oh, such a terrible night of worry! No word—and I called up the museum, but Doctor Bernardo, the curator, had gone, and no one answered. And this morning—I couldn't stand it any longer—so I came to you."

"You have no idea, I suppose, of anything that was weighing on his mind?" suggested Kennedy.

"No," she answered promptly.

In default of any further information, Kennedy did not pursue this line of questioning. I could not determine from his face or manner whether he thought the matter might involve another than Mrs. Northrop, or, perhaps, something connected with the unsettled condition of the country from which her husband had just arrived.

"Have you any of the letters that Archer wrote home?" asked Craig, at length.

"Yes," she replied eagerly, taking a little packet from her handbag. "I thought you might ask that. I brought them."

"You are an ideal client," commented Craig encouragingly, taking the letters. "Now, Mrs. Northrop, be brave. Trust me to run this thing down, and if you hear anything let me know immediately."

She left us a moment later, visibly relieved.

Scarcely had she gone when Craig, stuffing the letters into his pocket unread, seized his hat, and a moment later was striding along toward the museum with his habitual rapid, abstracted step which told me that he sensed a mystery.

In the museum we met Doctor Bernardo, a man slightly older than Northrop, with whom he had been very intimate. He had just arrived and was already deeply immersed in the study of some new and beautiful colored plates from the National Museum of Mexico City.

"Do you remember seeing Northrop here yesterday afternoon?" greeted
Craig, without explaining what had happened.

"Yes," he answered promptly. "I was here with him until very late. At least, he was in his own room, working hard, when I left."

"Did you see him go?"

"Why—er—no," replied Bernardo, as if that were a new idea. "I left him here—at least, I didn't see him go out."

Kennedy tried the door of Northrop's room, which was at the far end, in a corner, and communicated with the hall only through the main floor of the museum. It was locked. A pass-key from the janitor quickly opened it.

Such a sight as greeted us, I shall never forget. There, in his big desk-chair, sat Northrop, absolutely rigid, the most horribly contorted look on his features that I have ever seen—half of pain, half of fear, as if of something nameless.

Kennedy bent over. His hands were cold.

Northrop had been dead at least twelve hours, perhaps longer. All night the deserted museum had guarded its terrible secret.

As Craig peered into his face, he saw, in the fleshy part of the neck, just below the left ear, a round red mark, with just a drop or two of now black coagulated blood in the center. All around we could see a vast amount of miscellaneous stuff, partly unpacked, partly just opened, and waiting to be taken out of the wrappings by the now motionless hands.

"I suppose you are more or less familiar with what Northrop brought back?" asked Kennedy of Bernardo, running his eye over the material in the room.

"Yes, reasonably," answered Bernardo. "Before the cases arrived from the wharf, he told me in detail what he had managed to bring up with him."

"I wish, then, that you would look it over and see if there is anything missing," requested Craig, already himself busy in going over the room for other evidence.

Doctor Bernardo hastily began taking a mental inventory of the stuff. While they worked, I tried vainly to frame some theory which would explain the startling facts we had so suddenly discovered.

Mitla, I knew, was south of the city of Oaxaca, and there, in its ruined palaces, was the crowning achievement of the old Zapotec kings. No ruins in America were more elaborately ornamented or richer in lore for the archeologist.

Northrop had brought up porphyry blocks with quaint grecques and much hieroglyphic painting. Already unpacked were half a dozen copper axes, some of the first of that particular style that had ever been brought to the United States. Besides the sculptured stones and the mosaics were jugs, cups, vases, little gods, sacrificial stones—enough, almost, to equip a new alcove in the museum.

Before Northrop was an idol, a hideous thing on which frogs and snakes squatted and coiled. It was a fitting piece to accompany the gruesome occupant of the little room in his long, last vigil. In fact, it almost sent a shudder over me, and if I had been inclined to the superstitious, I should certainly have concluded that this was retribution for having disturbed the lares and penates of a dead race.

Doctor Bernardo was going over the material a second time. By the look on his face, even I could guess that something was missing.

"What is it?" asked Craig, following the curator closely.

"Why," he answered slowly, "there was an inscription—we were looking at it earlier in the day—on a small block of porphyry. I don't see it."

He paused and went back to his search before we could ask him further what he thought the inscription was about.

I thought nothing myself at the time of his reticence, for Kennedy had gone over to a window back of Northrop and to the left. It was fully twenty feet from the downward slope of the campus there, and, as he craned his neck out, he noted that the copper leader of the rain pipe ran past it a few feet away.

I, too, looked out. A thick group of trees hid the window from the avenue beyond the campus wall, and below us, at a corner of the building, was a clump of rhododendrons. As Craig bent over the sill, he whipped out a pocket lens.

A moment later he silently handed the glass to me. As nearly as I could make out, there were five marks on the dust of the sill.

"Finger-prints!" I exclaimed. "Some one has been clinging to the edge of the ledge."

"In that case," Craig observed quietly, "there would have been only four prints."

I looked again, puzzled. The prints were flat and well separated.

"No," he added, "not finger-prints—toe-prints."

"Toe-prints?" I echoed.

Before he could reply, Craig had dashed out of the room, around, and under the window. There, he was carefully going over the soft earth around the bushes below.

"What are you looking for?" I asked, joining him.

"Some one—perhaps two—has been here," he remarked, almost under his breath. "One, at least, has removed his shoes. See those shoe-prints up to this point? The print of a boot-heel in soft earth shows the position and contour of every nail head. Bertillon has made a collection of such nails, certain types, sizes, and shapes used in certain boots, showing often what country the shoes came from. Even the number and pattern are significant. Some factories use a fixed number of nails and arrange them in a particular manner. I have made my own collection of such prints in this country. These were American shoes. Perhaps the clue will not lead us anywhere, though, for I doubt whether it was an American foot."

Kennedy continued to study the marks.

"He removed his shoes—either to help in climbing or to prevent noise—ah—here's the foot! Strange—see how small it is—and broad, how prehensile the toes—almost like fingers. Surely that foot could never have been encased in American shoes all its life. I shall make plaster casts of these, to preserve later."

He was still scouting about on hands and knees in the dampness of the rhododendrons. Suddenly he reached his long arm in among the shrubs and picked up a little reed stick. On the end of it was a small cylinder of buff brown.

He looked at it curiously, dug his nail into the soft mass, then rubbed his nail over the tip of his tongue gingerly.

With a wry face, as if the taste were extremely acrid, he moistened his handkerchief and wiped off his tongue vigorously.

"Even that minute particle that was on my nail makes my tongue tingle and feel numb," he remarked, still rubbing. "Let us go back again. I want to see Bernardo."

"Had he any visitors during the day?" queried Kennedy, as he reentered the ghastly little room, while the curator stood outside, completely unnerved by the tragedy which had been so close to him without his apparently knowing it. Kennedy was squeezing out from the little wound on Northrop's neck a few drops of liquid on a sterilized piece of glass.

"No; no one," Bernardo answered, after a moment.

"Did you see anyone in the museum who looked suspicious?" asked
Kennedy, watching Bernardo's face keenly.

"No," he hesitated. "There were several people wandering about among the exhibits, of course. One, I recall, late in the afternoon, was a little dark-skinned woman, rather good-looking."

"A Mexican?"

"Yes, I should say so. Not of Spanish descent, though. She was rather of the Indian type. She seemed to be much interested in the various exhibits, asked me several questions, very intelligently, too. Really, I thought she was trying to—er—flirt with me."

He shot a glance at Craig, half of confession, half of embarrassment.

"And—oh, yes—there was another—a man, a little man, as I recall, with shaggy hair. He looked like a Russian to me. I remember, because he came to the door, peered around hastily, and went away. I thought he might have got into the wrong part of the building and went to direct him right—but before I could get out into the hall, he was gone. I remember, too, that, as I turned, the woman had followed me and soon was asking other questions—which, I will admit—I was glad to answer."

"Was Northrop in his room while these people were here?"

"Yes; he had locked the door so that none of the students or visitors could disturb him."

"Evidently the woman was diverting your attention while the man entered Northrop's room by the window," ruminated Craig, as we stood for a moment in the outside doorway.

He had already telephoned to our old friend Doctor Leslie, the coroner, to take charge of the case, and now was ready to leave. The news had spread, and the janitor of the building was waiting to lock the campus door to keep back the crowd of students and others.

Our next duty was the painful one of breaking the news to Mrs. Northrop. I shall pass it over. Perhaps no one could have done it more gently than Kennedy. She did not cry. She was simply dazed. Fortunately her mother was with her, had been, in fact, ever since Northrop had gone on the expedition.

"Why should anyone want to steal tablets of old Mixtec inscriptions?" I asked thoughtfully, as we walked sadly over the campus in the direction of the chemistry building. "Have they a sufficient value, even on appreciative Fifth Avenue, to warrant murder?"

"Well," he remarked, "it does seem incomprehensible. Yet people do just such things. The psychologists tell us that there is a veritable mania for possessing such curios. However, it is possible that there may be some deeper significance in this case," he added, his face puckered in thought.

Who was the mysterious Mexican woman, who the shaggy Russian? I asked myself. Clearly, at least, if she existed at all, she was one of the millions not of Spanish but of Indian descent in the country south of us. As I reasoned it out, it seemed to me as if she must have been an accomplice. She could not have got into Northrop's room either before or after Doctor Bernardo left. Then, too, the toe-and shoe-prints were not hers. But, I figured, she certainly had a part in the plot.

While I was engaged in the vain effort to unravel the tragic affair by pure reason, Kennedy was at work with practical science.

He began by examining the little dark cylinder on the end of the reed. On a piece of the stuff, broken off, he poured a dark liquid from a brown-glass bottle. Then he placed it under a microscope.

"Microscopically," he said slowly, "it consists almost wholly of minute, clear granules which give a blue reaction with iodine. They are starch. Mixed with them are some larger starch granules, a few plant cells, fibrous matter, and other foreign particles. And then, there is the substance that gives that acrid, numbing taste." He appeared to be vacantly studying the floor.

"What do you think it is?" I asked, unable to restrain myself.

"Aconite," he answered slowly, "of which the active principle is the deadly poisonous alkaloid, aconitin."

He walked over and pulled down a well-thumbed standard work on toxicology, turned the pages, then began to read aloud:

Pure aconitin is probably the most actively poisonous substance with which we are acquainted and, if administered hypodermically, the alkaloid is even more powerfully poisonous than when taken by the mouth.

As in the case of most of the poisonous alkaloids, aconitin does not produce any decidedly characteristic post-mortem appearances. There is no way to distinguish it from other alkaloids, in fact, no reliable chemical test. The physiological effects before death are all that can be relied on.

Owing to its exceeding toxic nature, the smallness of the dose required to produce death, and the lack of tests for recognition, aconitin possesses rather more interest in legal medicine than most other poisons.

It is one of the few substances which, in the present state of toxicology, might be criminally administered and leave no positive evidence of the crime. If a small but fatal dose of the poison were to be given, especially if it were administered hypodermically, the chances of its detection in the body after death would be practically none.