Perhaps an hour later our laboratory door was flung open suddenly, and both Kennedy and I leaped to our feet.

There was Inez Mendoza, alone, pale and agitated.

"Tell me, Professor Kennedy," she cried, her hands clasped before her in frantic appeal, "tell me—it isn't true—is it? He wasn't there—no—no—no!"

She would have fainted if Craig had not sprung forward and caught her in time to place her in our only easy-chair.

"Walter," he said, "quick—that bottle of aromatic spirits of ammonia over there—the second from the left."

I handed it to him, and threw open the window to allow the fresh air to blow in. As I did so one of the papers Kennedy had been studying blew off the table, and, as luck would have it, fell almost before her. She saw it, and in her hypersensitive condition recognized it instantly.

"Oh—that anonymous letter!" she cried. "Tell me—you do not think that—the friend of my father's that it warned me to beware of—was—"

She did not finish the sentence. She did not need to do so.

"Please, Senorita," pleaded and soothed Kennedy, "try to be calm. What has happened? Tell me. What is it?"

The ammonia and the fresh air seemed to have done their work, for she managed to brace herself, gripping the arms of the chair tightly and looking up searchingly into Craig's face.

"It's about Chester," she managed to gasp; then seemed unable to go on.

It was the first time I had ever heard her use Lockwood's first name, and I knew that something had stirred her emotions more deeply than at any time since the death of her father.

"Yes," prompted Kennedy. "Go on."

"I have heard that you found foot-prints, shoe-prints, in the dust in the Museum after the dagger was stolen," she said, speaking rapidly, suppressing her feelings heroically. "Since then you have been collecting prints of shoes—and I've heard that the shoe-prints that were found are those of—of Mr. Lockwood. Oh, Professor Kennedy, it cannot be—there must be some mistake."

For a moment Kennedy did not say anything. He was evidently seeking some way in which to lead up to the revelation of the truth without too much shock.

"You remember that time in the tea room when we were sitting with
Senora de Moche?" he asked finally.

"Yes," she said shortly, as though the very recollection were disagreeable to her.

Kennedy, however, had a disagreeable task, and he felt that it must be performed in the kindest manner.

"You remember then that she said she had one thing more to say, that it was about Mr. Whitney and Mr. Lockwood."

She was about to interrupt, but he hurried on, giving her no chance to do so. "She asked you to think it over. Suppose they did not have the dagger, she said. Then were their chances of finding the treasure any better than any one else had? And if they did have it, she asked what that meant. It is a dilemma, my dear Senorita, which you must meet some time. Why not meet it now?"

Her face was set. "You will remember, also, Professor Kennedy," she said, with a great effort controlling her voice, "that I said that Mr. Lockwood was not there to defend himself and I would not have him attacked by innuendo. I meant it to the Senora—I mean it to you!"

She had also meant it to defy him; but as she proceeded her voice broke, and before she knew it her nature had triumphed, and she was alternately sobbing and pleading.

For a minute or two Kennedy let her give vent to her emotions.

"It cannot be. It cannot be," she sobbed over and over. "He could not have been there. He could not have done it."

It was a terrible thing to have to disillusion her, but it was something now that had to be done. Kennedy had not sought to do so. He had postponed it in the hope of finding some other way. But now the thing was forced upon him.

"Who told you?" he asked finally.

"I was trying to read, to keep my mind occupied, as you asked me, when Juanita told me that there was some one in the living room who wanted to see me—a man. I thought it was either you or Mr. Jameson. But it was—Professor Norton—"

Kennedy and I exchanged glances. That was the action in revenge to Lockwood and Whitney which he had contemplated over the telephone. It was so cruel and harsh that I could have hated him for it, the more so as I recollected that it was he himself who had cautioned us against doing the very thing which now he had done in the heat of passion.

"Oh," she wailed, "he was very kind and considerate about it. He said he felt that it was his duty to tell me, that he would be anything, like an older brother, to me; that he could not see me blinded any longer to what was going on, and everybody knew, but had not love enough for me to tell. It was such a shock. I could not even speak. I simply ran from the room without another word to him, and Juanita found me lying on the bed. Then—I decided—I would come to you."

She paused, and her great, deep eyes looked up pathetically. "And you," she added bitterly, "you are going to tell me that he was right, that it is true. You can't prove it. Show me what it is that you have. I defy you!"

Somehow, as she rested and relieved her feelings, a new strength seemed to come to her. It was what Kennedy had been waiting for, the reaction that would leave her able for him to go on and plan for the future.

He reached into a drawer of a cabinet and pulled out the various shoe-prints which he had already shown Norton, and which he had studied and restudied so carefully.

"That is the print of the shoe in the dust of the Egyptian sarcophagus of the Museum," he said quietly. "Some one got in during the daytime and hid there until the place was locked. That is the print of Alfonso de Moche's shoe, that of Mr. Whitney's, and that of Mr. Lockwood's."

He said it quickly, as though trying to gloss it over. But she would not have it that way. She felt stronger, and she was going to see just what there was there. She took the prints and studied them, though her hand trembled. Hers was a remarkable mind. It took only seconds to see what others would have seen only in minutes. But it was not the reasoning faculty that was aroused by what she saw. It sank deep into her heart.

She flung the papers down.

"I don't believe it!" she defied. "There is some mistake. No—it cannot be true!"

It was a noble exhibition of faith. I think I have never seen any instant more tense than that in Kennedy's laboratory. There stood the beautiful girl declaring her faith in her lover, rejecting even the implication that it might have been he who had taken the dagger, perhaps murdered her father to insure the possession of her father's share of the treasure as well as the possession of herself.

Kennedy did not try to combat it. Instead he treated her very intuitions with respect. In him there was room for both fact and feeling.

"Senorita," he said finally, in a voice that was deep and thrilling with feeling, "have I ever been other than a friend to you? Have I ever given you cause to suspect even one little motive of mine?"

She faced him, and they looked into each other's eyes an instant. But it was long enough for the man to understand the woman and she to understand him.

"No," she murmured, glancing down again.

"Then trust me just this once. Do as I ask you."

For an instant she struggled with herself. What would he ask?

"What is it?" she questioned, raising her eyes to him again.

"Have you seen Mr. Lockwood?"

"No."

"Then, I want you to see him. Surely you wish to have no secrets from him any more than you would wish him to have anything secret from you. See him. Ask him frankly about it all. It is the only fair thing to him—it is only fair to yourself."

Senorita Mendoza was no coward. "I—I will," she almost whispered.

"Splendid!" exclaimed Kennedy in admiration. "I knew that you would. You are not the woman who could do otherwise. May I see that you get home safely? Walter, call a taxicab."

Senorita Mendoza was calmer, though pale and still nervous, when I returned. Kennedy handed her into the car and then returned to the laboratory for two rather large packages, which he handed to me.

"You must come along with us, Walter," he said. "We shall need you."

Scarcely a word was spoken as we jolted over the city pavements and at last reached the apartment. Inez and Craig entered and I followed, carrying just one of the packages as Craig had indicated by dumb show, leaving the other in the car, which was to wait.

"I think you had better write him a note," suggested Craig, as we entered the living room. "I don't want you to see him until you feel better—and, by the way, see him here."

She nodded with a wan smile, as though thinking how unusual it was for a meeting of lovers to be an ordeal, then excused herself to write the note.

She had no sooner disappeared than Kennedy unwrapped the package which I had brought. From it he took a cedar box, oblong, with a sort of black disc fixed to an arm on the top. In the face of the box were two little square holes, with sides of cedar which converged inward into the box, making a pair of little quadrangular pyramidal holes which ended in a small black circle in the interior.

He looked about the room quickly. Beside a window that opened out over a house several stories below stood a sectional bookcase. Into this bookcase, back of the books, in the shadow, he shoved the little box, to which he had already attached a spool of twisted wires. Then he opened the window and dropped the spool out, letting it unwind of its own weight until it fell on the roof far below. He shut the window and rejoined me without a word.

A moment later she returned with the dainty note which she had written.
"Shall I send it by a messenger?" she asked.

"Yes, please," answered Kennedy, rising. As he moved a step to the door he held out his hand to her. "Senorita Mendoza," he said simply, in a tone that meant more than words, "you are a wonderful woman."

She took his hand without a word, and a moment later we were whisked down in the elevator.

"I must get on that roof on some pretext," remarked Kennedy, as we reached the street and he got his bearings. "Let me see, that house which backs up to the apartment is around the corner. Have the man drive us around there."

We located the house and mounted the steps. On the wall beside the brownstone door was pasted a little slip of paper, "Furnished Rooms."

"Splendid!" exclaimed Kennedy, as he read it. "Dismiss the taxi and meet me inside with the other package."

By the time I had paid the man and come up the steps again Kennedy had made a dicker with the landlady for a double room on the third floor for both of us, and, by payment of a week's rent, we were to have immediate possession.

"Our baggage will follow to-day," he explained, as we mounted the stairs to the room.

I thought the landlady would never get through expatiating upon what a select place she ran, and thus leave us alone in our room, but at last even her flood of words was stilled by demands from a servant downstairs who must be instructed if the selectness of the establishment were to be maintained.

No sooner were we alone than Kennedy tiptoed into the hall and made sure that we were not watched. It was then the work of only a few seconds to mount a ladder to a scuttle, unhook it, and gain the roof.

There, dangling down from the dizzy height above, swayed the twisted wire. He seized it, unrolled it some more, and sent me downstairs to catch it, as he swung it over the edge of the roof to one of our own windows. Then he rejoined me.

The other package, which had been heavier, consisted of another of those mysterious boxes, as well as several dry cells. Quickly he attached the wires to the box, placing the dry cells in the circuit. Then he began adjusting the mechanism of the box. So far I had only a vague idea of just what he had in mind, but gradually it began to dawn on me.

It was perhaps half an hour, perhaps longer, after we had left the Senorita, before, sure that everything was all right with his line and the batteries which he had brought, Kennedy turned a little lever that moved in a semicircle, touching one after another of a series of buttons on the face of the cedar box, meanwhile holding a little black disc from the back of the box to his ear as he adjusted the thing.

Nothing seemed to happen, but I could tell by the look of intentness on his face that he was getting along all right and was not worrying.

Suddenly the look on his face changed to one of extreme satisfaction. He dropped the disc he was holding to his ear back into its compartment and turned to me.

All at once it seemed as if the room in which we were was peopled by spirits. There was the sound of voices, loud, clear, distinct. It was uncanny.

"He has just come in," remarked Craig.

"Who?" I asked.

"Lockwood—can't you recognize his voice? Listen."

I did listen intently, and the more my ears became adjusted, the more plainly I could distinguish two voices, that of a man and that of a woman. It was indeed Lockwood and the Senorita, far above us.

I would have uttered an exclamation of amazement, but I could not miss what they were saying.

"Then you—you believe what he says?" asked Lockwood earnestly.

"Professor Kennedy has the prints," replied Inez tremulously.

"You saw them?"

"Yes."

"And you believe what HE says, too?"

There was a silence.

"What is it?" I asked, tapping the box lightly.

"A vocaphone," replied Kennedy. "The little box that hears and talks."

"Can they hear us?" I asked, in an awestruck whisper.

"Not unless I want them to hear," he replied, indicating a switch. "You remember, of course, the various mechanical and electrical ears, such as the detectaphone, which we have used for eavesdropping in other cases?"

I nodded.

"Well, this is a new application which has been made of the detectaphone. When I was using that disc from the compartment there, I had really a detectaphone. But this is even better. You see how neat it all is? This is the detective service, and more. We can 'listen in' and we don't have to use ear-pieces, either, for this is a regular loud-speaking telephone—it talks right out in meeting. Those square holes with the converging sides act as a sort of megaphone to the receivers, those little circles back there inside magnifying the sound and throwing it out here in the room, so that we can hear just as well as if we were up there in the room where they are talking. Listen—I think they are talking again."

"I suppose you know that Whitney and I have placed detectives on the trail of Norton," we could hear Lockwood say.

"You have?" came back the answer in a voice which for the first time sounded cold.

Lockwood must have recognized it. He had made a mistake. It was no sufficient answer to anything that he had done to assert that some one else had also done something.

"Inez," he said, and we could almost hear his feet as he moved over the floor in her direction in a last desperate appeal, "can't you trust me, when I tell you that everything is all right, that they are trying to ruin me—with you?"

There was a silence, during which we could almost hear her quick breath come and go.

"Women—not even Peruvian women are like the women of the past, Chester," she said at length. "We are not playthings. Perhaps we have hearts—but we also have heads. We are not to be taken up and put down as you please. We may love—but we also think. Chester, I have been to see Professor Kennedy, and—"

She stopped. It hurt too much to repeat what she had seen.

"Inez," he implored.

There was evidently a great struggle of love and suspicion going on in her, her love of him, her memory of her father, the recollection of what she had heard and seen. No one could have been as we were without wishing to help her. Yet no one could help her. She must work out her own life herself.

"Yes," she said finally, the struggle ended. "What is it?"

"Do you want me to tell you the truth?"

"Yes," she murmured.

His voice was low and tense.

"I was there—yes—but the dagger was gone!"