Part 34 (1/2)

”You have been on a bust,” he said with a smile as if the remark of a few minutes before were still fresh. ”Only it was a laughing gas jag--nitrous oxide.”

”Nitrous oxide?” I repeated. ”How--what do you mean?”

”I mean simply that a test of your blood shows that you were poisoned by nitrous oxide gas. You remember the sample of blood which I squeezed from your thumb? I took it because I knew that a gas--and it has proved to be nitrous oxide--is absorbed through the lungs into the circulation and its presence can be told for a considerable period after administration.”

He paused a moment, then went on: ”To be specific in this case I found by microscopic examination that the number of corpuscles in your blood was vastly above the normal, something like between seven and eight million to a drop that should have had somewhat more than only half that number. You were poisoned by gas that--”

”Yes,” I interrupted, ”but how, with all the doors locked?”

”I was coming to that,” he said quietly, picking up the lock and looking at it thoughtfully.

He had already placed it in a porcelain basin, and in this basin he had poured some liquids. Then he pa.s.sed the liquids through a fine screen and at last took up a tube containing some of the resulting liquid.

”I have already satisfied myself,” he explained, ”but for your benefit, seeing that you're the chief sufferer, I'll run over a part of the test. You saw the reaction which showed the gas a moment ago. I have proved chemically as well as microscopically that it is present in your blood. Now if I take this test-tube of liquid derived from my treatment of the lock and then test it as you saw me do with the other, isn't that enough for you? See--it gives the same reaction.”

It did, indeed, but my mind did not react with it.

”Nitrous oxide,” he continued, ”in contact with iron, leaves distinct traces of corrosion, discernible by chemical and microscopic tests quite as well as the marks it leaves in the human blood. Manifestly, if no one could have come in by the windows or doors, the gas must have been administered in some way without any one coming into the room. I found no traces of an intruder.”

It was a tough one. Never much good at answering his conundrums when I was well, I could not even make a guess now.

”The key-hole, of course!” he explained. ”I cut away the entire lock, and have submitted it to these tests which you see.”

”I don't see it all yet,” I said.

”Some one came to our door in the night, after gaining entrance to the hall--not a difficult thing to do, we know. That person found our door locked, knew it would be locked, knew that I always locked it. Knowing that such was the case, this person came prepared, bringing perhaps, a tank of compressed nitrous oxide, certainly the materials for making the gas expeditiously.”

I began to understand how it had been done.

”Through the keyhole,” he resumed, ”a stream of the gas was injected.

It soon rendered you unconscious, and that would have been all, if the person had been satisfied. A little bit would have been harmless enough. But the person was not satisfied. The intention was not to overcome, but to kill. The stream of gas was kept up until the room was full of it.

”Only my return saved you, for the gas was escaping very slowly. Even then, you had been under it so long that we had to resort to the wonderful little pulmotor after trying both the Sylvester and Schaefer methods and all other manual means to induce respiration. At any rate we managed to undo the work of this fiend.”

I looked at him in surprise, I, who didn't think I had an enemy in the world.

”But who could it have been?” I asked.

”We are pretty close to that criminal,” was the only reply he would give, ”providing we do not spread the net in sight of the quarry.”

”Why should he have wanted to get me?” I repeated.

”Don't flatter yourself,” replied Craig. ”He wanted me, too. There wasn't any light in the laboratory last night. There was a light in our apartment. What more natural than to think that we were both there? You were caught in the trap intended for both of us.”

I looked at him, startled. Surely this was a most desperate criminal.

To cover up one murder--perhaps two--he did not hesitate to attempt a third, a double murder. The attack had been really aimed at Kennedy. It had struck me alone. But it had miscarried and Craig had saved my life.

As I reflected bitterly, I had but one satisfaction. Wretched as I felt, I knew that it had spared Craig from slowing up on the case at just the time when he was needed.