“Don’t you want more light?” I asked, starting to cross to a window to let the moonlight stream in.

“Don’t walk on it, Walter,” he whispered, pushing me back.  “No, I don’t need any more light.”

“What are you doing?” I asked, mystified at his actions.

“First I sprinkled some powdered iodine on the floor,” he replied, “and then sprayed over just enough ammonia to moisten it.  It will evaporate quickly, leaving what I call my anti-burglar powder.”

“I’m sure I wouldn’t be thought one of the fraternity for the world,” I observed, stepping aside to give him all the room he wanted in which to operate.

He had finished his work by this time and now the evening wind was blowing away the slight fumes that had arisen.  For a few moments he left our door into Whitney’s room open, in order to insure clearing away the odour.  Then he quietly closed it, but did not lock it again.

We waited a few minutes, then Craig leaned over to me.  “I wish you’d go down and see how near Whitney is through dinner,” he said.  “If he is through, do something, anything to keep him down there.  Only be as careful as you can not to be seen by any one who knows us.”

I rode down in an empty elevator and cautiously made my way to the dining-room.  Whitney had finished much sooner than I had expected and was not there.  Much as I wanted not to be seen, I found that it was necessary to make a tour of the hotel to find him and I did so, wondering what expedient I would adopt to keep him down there if I found him.  I did not have to adopt any, however.  Whitney was almost alone in the writing-room, and a big pile of letters beside him showed me that he would be busy for some time.  I rode back to the room to tell Craig, flattering myself that I had not been seen.

“Good,” he exclaimed.  “I don’t think we’ll have to wait much longer, if anything at all is going to happen.”

In the darkness we settled ourselves for another vigil that was to last we knew not how long.  Neither of us spoke as we half crouched in the shadow of our room, listening.

Slowly the time passed.  Would any one take advantage of the opportunity to tamper with the box of cigarettes on the table?

I fell to speculating.  Who could it possibly have been that had conceived this devilish plot?  What was back of it all?  I wondered whether it were possible that Lockwood, now that Mendoza was out of the way, could desire to remove Whitney, the sole remaining impediment to possessing the whole of the treasure as well as Inez?  Then there were the Senora and Alfonso, the one with a deep race and family grievance, the other a rejected suitor.  What might not they do with some weird South American poison?

Once or twice we heard the elevator door clang and waited expectantly, but nothing happened.  I began to wonder whether, even if some one had a pass-key to the suite, we could hear him enter if he was quiet.  The outside hall was thickly carpeted, and deadened every footfall if one exercised only reasonable care.  The rooms themselves were much the same.