Norton was waiting for us at the laboratory when we returned, evidently having been there some time.

"I was on my way to my apartment," he began, "when I thought I'd drop in to see how things are progressing."

"Slowly," returned Kennedy, throwing off his street clothes and getting into his laboratory togs.

"Have you seen Whitney since I had the break with him?" asked Norton, a trifle anxiously.

I wondered whether Kennedy would tell Norton what to expect from
Whitney. He did not, however.

"Yes," he replied, "just now we had an appointment with Senora de Moche and some others and ran into him at the hotel for a few moments."

"What did he say about me?" queried Norton.

"He hadn't changed his mind," evaded Kennedy. "Have you heard anything from him?"

"Not a syllable. The break is final. Only I was wondering what he was telling people about me. He'll tell them something—his side of the case."

"Well," considered Kennedy, as though racking his brain for some remark which he remembered, while Norton watched him eagerly, "I do recall that he was terribly sore about the loss of the dagger, and seemed to think that it was your fault."

"I thought so, I knew it," replied Norton bitterly. "I can see it coming. All the trustees will hear of my gross negligence in letting the Museum be robbed. I suppose I ought to sit up there all night. Oh, by the way, there's another thing I wanted to ask you. Have you ever done anything with those shoe-prints you found in the dust of the mummy case?"

I glanced at Kennedy, wondering whether he felt that the time had come to reveal what he had discovered. He said nothing for a moment, but reached into a drawer and pulled out the papers, which I recognized.

"Here they are," he said, picking out the original impression which he had taken.

"Yes," repeated Norton, "but have you been able to do anything toward identifying them?"

"I found it rather hard to collect prints of the shoes of all of those
I wished to compare. But I have them at last."

"And?" demanded Norton, leaning forward tensely.

"I find that there is one person whose shoe-prints are precisely the same as those we found in the Museum," went on Kennedy, tossing over the impression he had taken.

Norton scanned the two carefully. "I'm not a criminologist," he said excitedly, "but to my untrained eye it does seem as though you had here a replica of the first prints, all right." He laid them down and looked squarely at Kennedy. "Do you mind telling me whose feet made these prints?"

"Turn the second over. You will see the name written on it."

"Lockwood!" exclaimed Norton in a gasp as he read the name. "No—you don't mean it."

"I mean nothing less," repeated Kennedy firmly. "I do not say what happened afterwards, but Lockwood was in the Museum, hiding in the mummy case, that night."

Norton's mind was evidently working rapidly. "I wish I had your power of deduction, Kennedy," he said, at length. "I suppose you realize what this means?"

"What does it mean to you?" asked Kennedy, changing front.

Norton hesitated. "Well," he replied, "it means to me, I suppose, what it means to any one who stops to think. If Lockwood was there, he got the dagger. If he had the dagger—it was he who used it!"

The inference was so strong that Craig could not deny it. Whether it was his opinion or not was another matter.

"It fits in with other facts, too," continued Norton. "For instance, it was Lockwood who discovered the body of Mendoza."

"But the elevator boy took Lockwood up himself," objected Craig, more for the sake of promoting the discussion than to combat Norton.

"Yes—when he 'discovered' the thing. But it must have been done long before. Who knows? He may have entered. The deed might have been done. He may have left. No one saw him come or go. What then more likely to cover himself up than to return when he knew that his entrance would be known, and find the thing himself?"

Norton's reasoning was clever and plausible. Yet Kennedy scarcely nodded his head, one way or the other.

"You were acquainted with Lockwood?" he asked finally. "I mean to say, of course, before this affair."

"Yes, I met him in Lima just as I was starting out on my expedition. He was preparing to come to New York."

"What did you think of him then?"

"Oh, he was all right, I suppose. He wasn't the sort who would care much for an archaeologist. He cared more for a prospector going off into the hills than he did for me. And I—I admit that I am impossible. Archaeology is my life."

Norton continued to study the prints. "I can hardly believe my eyes," he murmured; then he looked up suddenly. "Does Whitney know about this—or Lockwood?"

Kennedy shook his head negatively.

"Because," pursued Norton, "an added inference to that I spoke of would be that the reason why they are so sure that they will find the treasure is that they are not going on tradition, as they say, but on the fact itself."

"A fair conclusion," agreed Craig.

"I wish the break could have been postponed," continued Norton. "Then I might have been of some service in my relation to Whitney. It's too late for me to be able to help you in that direction now, however."

"There is something you can do, though," said Craig.

"I shall be delighted," hastened Norton. "What is it?"

"You know Senora de Moche and Alfonso?"

"Yes."

"I wish that you would cultivate their acquaintance. I feel that they are very suspicious of me. Perhaps they may not be so with you."

"Is there any special thing you want to find out?"

"Yes—only I have slight hopes of doing so. You know that she is on most intimate terms with Whitney."

"I'm afraid I can't do much for you, then. She'll fight shy of me.
He'll tell her his story."

"That will make no difference. She has already warned me against him. He has warned against her. It's a most remarkable situation. He is trying to get her into some kind of deal, yet all the time he is afraid she is double-crossing him. And at the same time he obeys her—well, like Alfonso would Inez if she'd only let him."

Norton frowned. "I don't like the way they hover about Inez Mendoza," he remarked. "Perhaps the Senora is after Whitney, while her son is after Inez. Lockwood seems to be impervious to her. Yes, I'll undertake that commission for you, only I can't promise what success I'll have."

Kennedy restored the shoe-prints to the drawer.

"I think that's gratifying progress," went on Norton. "First we know who stole the dagger. We know that the dagger killed Mendoza. You have even determined what the poison on the blade was. It seems to me that it remains only to determine who struck the actual blow. I tell you, Kennedy, Whitney will regret the day that he ever threw me over on so trivial a pretext."

Norton was pacing up and down excitedly now.

"My only fear is," he went on, "what the shock of such a thing will be on that poor little girl. First her father, then Lockwood. Why—the blow will be terrible. You must be careful, Kennedy."

"Never fear about that," reassured Craig. "Not a word of this has been breathed to her yet. We are a long way from fixing the guilt of the murder; inference is one thing, fact another. We must have facts. And the facts I want, which you may be able to get, relate to the strange actions of the de Moches."

Norton scanned Kennedy's face for some hint of what was back of the remark. But there was nothing there.

"They will bear watching, all right," he said, as he rose to go. "Old
Mendoza was never quite the same after he became so intimate with her.
And I think I can see a change in Whitney."

"What do you attribute it to?" asked Kennedy, without admitting that it had attracted his attention, too.

"I haven't the slightest idea," confessed Norton.

"Inez is as afraid of her as any of the rest," remarked Kennedy thoughtfully. "She says it is the evil eye."

"Not an uncommon belief among Latin-Americans," commented Norton. "In fact, I suppose there are people among us who believe in the evil eye yet. Still, you can hardly blame that little girl for believing it is almost anything. Well, I won't keep you any longer. I shall let you know of anything I find out from the de Moches. I think you are getting on remarkably."

Norton left us, his face much brighter than it had been when we met him at the door.

Kennedy, alone at last in the laboratory, went over to a cabinet and took out a peculiar-looking apparatus, which seemed, as nearly as I can describe it, to consist of a sort of triangular prism, set with its edge vertically on a rigid platform attached to a massive stand of brass.

"Norton seems to have suddenly become quite solicitous of the welfare of Senorita Mendoza," I hazarded, as he worked over the adjustment of the thing.

Kennedy smiled. "Every one seems to be—even Whitney," he returned, twisting a set-screw until he had the alignment of the various parts as he wanted it.

The telephone bell rang.

"Do you want to answer it?" I asked Craig.

"No," he replied, not even looking up from his work. "Find out who it is. Unless it is something very important say I am out on an investigation and that you have heard from me; that I shall not be either at the laboratory or the apartment until tomorrow morning. I must get this done to-night."

I took down the receiver.

"Hello, is this Professor Kennedy?" I recognized a voice.

"No," I replied. "Is there any message I can take?"

"This is Mr. Lockwood," came back the information I had already guessed. "When do you expect him?"

"It's Lockwood," I whispered to Craig, my hand over the transmitter.

"See what he wants," returned Craig. "Tell him what I told you."

I repeated Kennedy's message.

"Well, that's too bad," replied Lockwood. "I've just seen Mr. Whitney, and he tells me that Kennedy and you are pretty friendly with Norton, Of course, I knew that. I saw you at the Mendozas' together the first time. I'd like to have a talk with him about that man. I suppose he has told you all his side of the story of his relations with Whitney."

I am, if anything, a good listener, and so I said nothing, not even that he had better tell it to Kennedy in the morning, for it was such a novelty to have any of these people talk voluntarily that I really didn't much care whether I believed what they said or not.

"I used to know him down in Lima, you know," went on Lockwood. "What I want to say has to do with that dagger he says was stolen. I want to tell what I know of how he got it. There was an Indian mixed up in it who committed suicide—well, you tell Kennedy I'll see him in the morning."

Lockwood rang off, and I repeated what he had told me, as Kennedy continued to adjust the apparatus.

"Say," I exclaimed, as I finished. "That was a harry's of a commission you gave Norton just now, watching the de Moches. Why, they'd eat him alive if they got a chance, and I don't know that all's like a Sunday school on his part. Lockwood doesn't seem to think so."

Kennedy smiled quietly. "That was why I asked him to do it," he returned. "I thought that he wouldn't let much escape him. They all seem so down on him, he'll have to watch out. It will keep him busy, too, and that means a chance for us to work."

He had finished setting up the machine, and now went over to another drawer, from which he took the envelope of stubs which we had taken down at Whitney's office first. Then from the pocket of his street coat he drew both the second envelope of ashes and stubs, the whole cigarette from Lockwood's case, and the stubs which both of us had saved from the cigarettes that had once belonged to Mendoza.

Carefully he separated and labelled them all, so that there would be no chance for them to get mixed up. Then he picked up one of the stubs and lighted it. The smoke curled up in wreaths between a powerful light and the peculiar instrument, while Craig peered through a lens, manipulating the thing with exhaustless patience and skill. I watched him curiously, but said nothing, for he was studying something carefully, and I did not want to interrupt his train of thought.

Finally he beckoned me over. "Can you make anything out of that?" he asked.

I looked through the eye-piece, also. On a sort of fine grating all I could see was a number of strange lines.

"If you want an opinion from me," I said, with a laugh, "you'll have to tell me first what I am looking at."

"That," he explained, as I continued to gaze, "is one of the latest forms of the spectroscope, known as the interferometer, with delicately ruled gratings in which power to resolve the straight, close lines in the spectrum is carried to the limit of possibility. A small watch is delicate. But it bears no comparison to the delicacy of these defraction spectroscopes.

"Every substance, you know, is, when radiating light, characterized by what at first appears to be almost haphazard sets of spectral bands without relation to one another. But they are related by mathematical laws, and the apparent haphazard character is only the result of our lack of knowledge of how to interpret the results."

He resumed his place at the eye-piece to check over his results.

"Walter," he said finally, looking up at me with a twinkle in his eye,
"I wish that you'd go out and find me a cat."

"A cat?" I repeated.

"Yes, a cat—felis domesticus, if it sounds better that way—a plain, ordinary cat."

I jammed on my hat and, late as it was, sallied forth on this apparently ridiculous mission.

Several belated passers-by and a policeman watched me as though I were a house-breaker, and I felt like a fool, but at last, by perseverance and tact, I managed to capture a fairly good specimen of the species, and carried it in my arms to the laboratory with some profanity and many scratches.