We could only stare at each other and at that tell-tale sign of the Inca dagger underneath.

What did it mean?  Who had sent the warnings?

Kennedy alone seemed to regard the affair as if with purely scientific interest.  He took the four pieces of paper and laid them down before him on the table.  Then he looked up suddenly.

“They match perfectly,” he said quietly, gathering them up and placing them in a wallet which he carried.  “All the indentures of the tearing correspond.  Four warnings seem to have been sent to those who are likely to find out something of the secret.”

Norton seemed to have gained somewhat of his composure now that he had been able to talk to some one.

“What are you going to do—­give it up?” he asked tensely.

“Nothing could have insured my sticking to it harder,” answered Craig grimly.

“Then we’ll all have to stick together,” said Norton slowly.  “We all seem to be in the same boat.”

As he rose to go he extended a hand to each of us.

“I’ll stick,” repeated Kennedy, with that peculiar bulldog look of intensity on his face which I had come to know so well.

IV

THE TREASURE HUNTERS

Norton had scarcely gone, and Kennedy was still studying the four pieces of paper on which the warning had been given, when our laboratory door was softly pushed open again.

It was Senorita Mendoza, looking more beautiful than ever in her plain black mourning dress, the unnatural pallor of her face heightening the wonderful lustrous eyes that looked about as though half frightened at what she was doing.

“I hope nothing has happened,” greeted Kennedy, placing an easy-chair for her.  “But I’m glad to see that you have confidence enough to trust me.”

She looked about doubtfully at the vast amount of paraphernalia which Craig had collected in his scientific warfare on crime.  Though she did not understand it, it seemed to impress her.

“No,” she murmured, “nothing new has happened.  You told me to call on you if I should think of anything else.”

She said it with an air as if confessing something.  It was apparent that, whatever it was, she had known it all the time and only after a struggle had brought herself to telling it.

“Then you have thought of something?” prompted Craig.

“Yes,” she replied in a low tone.  Then with an effort she went on:  “I don’t know whether you know it or not, but my family is an old one, one of the oldest in Peru.”

Kennedy nodded encouragingly.

“Back in the old days, after Pizarro,” she hurried on, no longer able to choose her words, but blurting the thing out directly, “an ancestor of mine was murdered by an Inca dagger.”

She stopped again and looked about, actually frightened at her own temerity, evidently.  Kennedy and his twentieth-century surroundings seemed again to reassure her.