As I looked at him nervously walking to and fro, I could not help admitting that things looked safe enough and all right to me.  Kennedy folded the periscope up and we left our room, mounting the remaining flight of stairs.

In fifty-nine we could hear the measured step of the footman.  Craig knocked.  The footsteps ceased.  Then the door opened slowly and I could see a cold blue automatic.

“Look out!” I cried.

Michael in his fear had drawn a gun.

“It’s all right, Michael,” reassured Craig calmly.  “All right, Walter,” he added to me.

The gun dropped back into the footman’s pocket.  We entered and Michael again locked the door.  Not a word had been spoken by him so far.

Next Michael moved to the center of the room and, as I realized later, brought himself in direct lines with the open window.  He seemed to be overcome with fear at his betrayal and stood there breathing heavily.

“Professor Kennedy,” he began, “I have been so mistreated that I have made up my mind to tell you all I know about this Clutching—­ "

Suddenly he drew a sharp breath and both his hands clutched at his own breast.  He did not stagger and fall in the ordinary manner, but seemed to bend at the knees and waist and literally crumple down on his face.

We ran to him.  Craig turned him over gently on his back and examined him.  He called.  No answer.  Michael was almost pulseless.

Quickly Craig tore off his collar and bared his breast, for the man seemed to be struggling for breath.  As he did so, he drew from Michael’s chest a small, sharp-pointed dart.

“What’s that?” I ejaculated, horror stricken.

“A poisoned blow gun dart such as is used by the South American Indians on the upper Orinoco,” he said slowly.

He examined it carefully.

“What is the poison?” I asked.

“Curari,” he replied simply.  “It acts on the respiratory muscles, paralyzing them, and causing asphyxiation.”

The dart seemed to have been made of a quill with a very sharp point, hollow, and containing the deadly poison in the sharpened end.

“Look out!” I cautioned as he handled it.

“Oh, that’s all right,” he answered casually.  “If I don’t scratch myself, I am safe enough.  I could swallow the stuff and it wouldn’t hurt me—­unless I had an abrasion of the lips or some internal cut.”

Kennedy continued to examine the dart until suddenly I heard a low exclamation of surprise from him.  Inside the hollow quill was a thin sheet of tissue paper, tightly rolled.  He drew it out and read: 

“To know me is death Kennedy—­Take Warning!”

Underneath was the inevitable Clutching Hand sign.

We jumped to our feet.  Kennedy rushed to the window and slammed it shut, while I seized the key from Michael’s pocket, opened the door and called for help.

A moment before, on the roof of a building across the street, one might have seen a bent, skulking figure.  His face was copper colored and on his head was a thick thatch of matted hair.  He looked like a South American Indian, in a very dilapidated suit of castoff American clothes.