"I know," I pursued, watching Kennedy's interest in our conversation, "but this was not tattooed."

"Well, then, it must have been false," insisted Bernardo.

The curator chatted a few moments, during which I expected Kennedy to lead the conversation around to Senora Herreria. But he did not, evidently fearing to show his hand.

"What did you make of it?" I asked, when he had gone. "Is he trying to hide something?"

"I think he has simplified the case," remarked Craig, leaning back, his hands behind his head, gazing up at the ceiling. "h.e.l.lo, here's Leslie!

What did you find, Doctor?" The coroner had entered with a look of awe on his face, as if Kennedy had directed him by some sort of necromancy.

"It was Senora Herreria!" he exclaimed. "She has been missing from the hotel ever since late yesterday afternoon. What do you think of it?"

"I think," replied Kennedy, speaking slowly and deliberately, "that it is very much like the Northrop case. You haven't taken that up yet?"

"Only superficially. What do you make of it?" asked the coroner.

"I had an idea that it might be aconitin poisoning," he said.

Leslie glanced at him keenly for a moment. "Then you'll never prove anything in the laboratory," he said.

"There are more ways of catching a criminal, Leslie," put in Craig, "than are set down in the medico-legal text-books. I shall depend on you and Jameson to gather together a rather cosmopolitan crowd here to-night."

He said it with a quiet confidence which I could not gainsay, although I did not understand. However, mostly with the official aid of Doctor Leslie, I followed out his instructions, and it was indeed a strange party that a.s.sembled that night. There were Doctor Bernardo; Sato, the curio dealer; Otaka, the Ainu, and ourselves. Mrs. Northrop, of course, could not come.

"Mexico," began Craig, after he had said a few words explaining why he had brought us together, "is full of historical treasure. To all intents and purposes, the government says, 'Come and dig.' But when there are finds, then the government swoops down on them for its own national museum. The finder scarcely gets a chance to export them.

However, now seemed to be the time to Professor Northrop to smuggle his finds out of the country.

"But evidently it could not be done without exciting all kinds of rumors and suspicions. Stories seem to have spread far and fast about what he had discovered. He realized the unsettled condition of the country--perhaps wanted to confirm his reading of a certain inscription by consultation with one scholar whom he thought he could trust. At any rate, he came home."

Kennedy paused, making use of the silence for emphasis. "You have all read of the wealth that Cortez found in Mexico. Where are the gold and silver of the conquistadores? Gone to the melting pot, centuries ago.

But is there none left? The Indians believe so. There are persons who would stop at nothing--even at murder of American professors, murder of their own comrades, to get at the secret."

He laid his hand almost lovingly on his powerful little microscope as he resumed on another line of evidence.

"And while we are on the subject of murders, two very similar deaths have occurred," he went on. "It is of no use to try to gloss them over.

Frankly, I suspected that they might have been caused by aconite poisoning. But, in the case of such poisoning, not only is the lethal dose very small but our chemical methods of detection are nil. The dose of the active principle, aconitin nitrate, is about one six-hundredth of a grain. There are no color tests, no reactions, as in the case of the other organic poisons."

I wondered what he was driving at. Was there, indeed, no test? Had the murderer used the safest of poisons--one that left no clue? I looked covertly at Sato's face. It was impa.s.sive. Doctor Bernardo was visibly uneasy as Kennedy proceeded. Cool enough up to the time of the mention of the treasure, I fancied, now, that he was growing more and more nervous.

Craig laid down on the table the reed stick with the little darkened cylinder on the end.

"That," he said, "is a little article which I picked up beneath Northrop's window yesterday. It is a piece of anno-noki, or bushi." I fancied I saw just a glint of satisfaction in Otaka's eyes.

"Like many barbarians," continued Craig, "the Ainus from time immemorial have prepared virulent poisons with which they charged their weapons of the chase and warfare. The formulas for the preparations, as in the case of other arrow poisons of other tribes, are known only to certain members, and the secret is pa.s.sed down from generation to generation as an heirloom, as it were. But in this case it is no longer a secret. It has now been proved that the active principle of this poison is aconite."

"If that is the case," broke in Doctor Leslie, "it is hopeless to connect anyone directly in that way with these murders. There is no test for aconitin."

I thought Sato's face was more composed and impa.s.sive than ever. Doctor Bernardo, however, was plainly excited.

"What--no test--NONE?" asked Kennedy, leaning forward eagerly. Then, as if he could restrain the answer to his own question no longer, he shot out: "How about the new starch test just discovered by Professor Reichert, of the University of Pennsylvania? Doubtless you never dreamed that starch may be a means of detecting the nature of a poison in obscure cases in criminology, especially in cases where the quant.i.ty of poison necessary to cause death is so minute that no trace of it can be found in the blood.

"The starch method is a new and extremely inviting subject to me. The peculiarities of the starch of any plant are quite as distinctive of the plant as are those of the hemoglobin crystals in the blood of an animal. I have a.n.a.lyzed the evidence of my microscope in this case thoroughly. When the arrow poison is introduced subcutaneously--say, by a person shooting a poisoned dart, which he afterward removes in order to destroy the evidence--the lethal const.i.tuents are rapidly absorbed.

"But the starch remains in the wound. It can be recovered and studied microscopically and can be definitely recognized. Doctor Reichert has published a study of twelve hundred such starches from all sorts of plants. In this case, it not only proves to be aconitin but the starch granules themselves can be recognized. They came from this piece of arrow poison."

Every eye was fixed on him now.

"Besides," he rapped out, "in the soft soil beneath the window of Professor Northrop's room, I found footprints. I have only to compare the impressions I took there and those of the people in this room, to prove that, while the real murderer stood guard below the window, he sent some one more nimble up the rain pipe to shoot the poisoned dart at Professor Northrop, and, later, to let down a rope by which he, the instigator, could gain the room, remove the dart, and obtain the key to the treasure he sought."

Kennedy was looking straight at Professor Bernardo.

"A friend of mine in Mexico has written me about an inscription," he burst out. "I received the letter only to-day. As nearly as I can gather, there was an impression that some of Northrop's stuff would be valuable in proving the alleged kinship between Mexico and j.a.pan, perhaps to arouse hatred of the United States."

"Yes--that is all very well," insisted Kennedy. "But how about the treasure?"

"Treasure?" repeated Bernardo, looking from one of us to another.

"Yes," pursued Craig relentlessly, "the treasure. You are an expert in reading the hieroglyphics. By your own statement, you and Northrop had been going over the stuff he had sent up. You know it."

Bernardo gave a quick glance from Kennedy to me. Evidently he saw that the secret was out.

"Yes," he said huskily, in a low tone, "Northrop and I were to follow the directions after we had plotted them out and were to share it together on the next expedition, which I could direct as a Mexican without so much suspicion. I should still have shared it with his widow if this unfortunate affair had not exposed the secret."

Bernardo had risen earnestly.

"Kennedy," he cried, "before G.o.d, if you will get back that stone and keep the secret from going further than this room, I will prove what I have said by dividing the Mixtec treasure with Mrs. Northrop and making her one of the richest widows in the country!"

"That is what I wanted to be sure of," nodded Craig. "Bernardo, Senora Herreria, of whom your friend wrote to you from Mexico, has been murdered in the same way that Professor Northrop was. Otaka was sent by her husband to murder Northrop, in order that they might obtain the so-called 'Pillar of Death' and the key to the treasure. Then, when the senora was no doubt under the influence of sake in the pretty little Oriental bower at the curio shop, a quick jab, and Otaka had removed one who shared the secret with them."

He had turned and faced the pair.

"Sato," he added, "you played on the patriotism of the senora until you wormed from her the treasure secret. Evidently rumors of it had spread from Mexican Indians to j.a.panese visitors. And then, Otaka, all jealousy over one whom she, no doubt, justly considered a rival, completed your work by sending her forth to die, unknown, on the street. Walter, ring up First Deputy O'Connor. The stone is hidden somewhere in the curio shop. We can find it without Sato's help. The quicker such a criminal is lodged safely in jail, the better for humanity."

Sato was on his feet, advancing cautiously toward Craig. I knew the dangers, now, of anno-noki, as well as the wonders of jujutsu, and, with a leap, I bounded past Bernardo and between Sato and Kennedy.

How it happened, I don't know, but, an instant later, I was sprawling.

Before I could recover myself, before even Craig had a chance to pull the hair-trigger of his automatic, Sato had seized the Ainu arrow poison from the table, had bitten the little cylinder in half, and had crammed the other half into the mouth of Otaka.

CHAPTER XIII

THE RADIUM ROBBER

Kennedy simply reached for the telephone and called an ambulance. But it was purely perfunctory. Dr. Leslie himself was the only official who could handle Sato's case now.