late prison was easily distinguished by the two holes in the door. We looked in; but that cellar was completely empty save for a few chips of wood and a pinch or two of sawdust; memorials of my sojourn in the lethal chamber at which I could hardly look without a shudder. Then we passed on to the next cellar—the one adjoining my prison—and this was an object of no little curiosity to me. Here, while I was securely bolted into my cell, that unknown villain had, deliberately and in cold blood, made all the arrangements for my murder; arrangements which he little suspected that I should survive to look upon.
Thorndyke, too, was interested. He stood at the open door, looking in as if considering the positions of various objects. As in fact he was. "Someone has been here since last night, Jervis," said he.
"Yes," agreed Jervis.
"That gas bottle has been taken down from the opening. You see, Jardine," he continued, "he had stood that big packing-case up on end and laid the gas bottle along the top, with its nozzle just opposite the hole. Two other bottles were standing upright with their nozzles upwards."
"I understand," said Thorndyke, "that you heard three bottles only turned on?"
"Yes," I answered; "there was the one opposite the hole and two others."
"I ask," Thorndyke said, "because there are, as you see, seven other bottles, lying by the wall. Those are all empty. We tried them when we came here last night."
"I know nothing about those others," said I. "The three bottles that I have mentioned I heard distinctly, and after he had turned on the third, the man went out of the cellar and closed up the door."
"Then," said Thorndyke, "the other seven were presumably used for some other—and let us hope, more legitimate—purpose. I wonder why our friend has been at the trouble of moving the cylinders."
"Perhaps," suggested Jervis, "he thought that the arrangement might be a little too illuminating for the police, if they should happen to pay a visit to the place. He may not be aware that the apparatus had already been inspected in situ by us. Or, again, the cylinders may have been moved by someone else. We are assuming that he is a lawful occupant of the premises; but he may be a mere secret intruder like ourselves, who has discovered that the place is more or less unoccupied and has made use of the premises and plant for his own benevolent purposes."
"Yes," agreed Thorndyke, "that is perfectly true. But we can put the matter to the test, at least negatively. If the cylinders have been moved by an innocent stranger they will bear the prints of hands."
"But why shouldn't the man himself leave the prints of his hands on the cylinders?" I asked.
"Because, my dear Jardine, he is too knowing a bird. Jervis and I went carefully over the cylinders last night in the hope of getting a few finger-prints to submit to Scotland Yard; but not a vestige could we find. Our friend had seen to that. We assumed that he had operated in gloves and your description of him confirmed our assumption. Which, in its way, is an interesting fact, for a man who is knowing enough to take these precautions has probably had some previous experience of crime, or, at least, has some acquaintance with the ways of criminals. The suggestion, in fact, is that, although this is not an ordinary professional crime, the perpetrator may be a professional criminal. And the further suggestion is, of course, that of very deliberate premeditation."
While he had been speaking he had produced from his pocket a small, flattened bottle fitted with a metal cap and filled with a yellowish powder. Removing the cap and uncovering a perforated inner cap, like that of an iodoform dredger, he proceeded to shake a cloud of the light powder over the three upper cylinders, jarring them with his foot to make the powder spread. Then he blew sharply on them, one after the other, when the powder disappeared from their surfaces, leaving visible one or two shapeless whitened smears but never a trace of a finger-print or even the shape of a hand.
Thorndyke rose and slipped the bottle back in his pocket. "Apparently," said he, "the cylinders were moved by our unknown friend, with the same careful precautions as on the first occasion. A wary gentleman, this, Jervis. He'll give us a run for our money, at any rate."
"Yes," agreed Jervis; "he doesn't mean to give himself away. He preserves his incognito most punctiliously. I'll say that for him."
"And meanwhile," said Thorndyke, "we had better proceed with our measures for drawing him out of this modest retirement. I want you, Jardine, to look round this cellar and tell us if any of the things that you see in it reminds you of anything that has happened to you, or suggests any thought or reflection."
I looked round, I am afraid rather vacantly. A more unsuggestive collection of objects I have never looked upon. "There are the gas cylinders," I said, feebly; "but I have told you about them. I don't see anything else excepting a few oddments of rubbish."
"Then take a good look at the rubbish," said he. "Remember that it may be necessary at some future time for you to recall exactly what this cellar was like, and what it contained. You may even have to make a sworn statement. So cast your eye round and tell us what you see."
I did so, wondering inwardly what the deuce I was expected to see and what might be the importance of my seeing it. "I see," said I, "a mouldy-looking cellar about fifteen feet by twelve, with very bad brick walls, a plaster ceiling in an advanced stage of decay, and a concrete floor. In the left hand wall is a hole about six inches square opening into the adjoining cellar. The contents are ten gas cylinders, all apparently empty, a key or spanner which seems to have been used to turn the cocks, a large packing-case, which, to judge by its shape, seems to have contained gas cylinders—"
"The word 'large,'" interrupted Thorndyke, " is not a particularly exact one."
"Well, then, a packing-case about seven feet long by two and a half feet wide and deep."
"That's better," said Thorndyke. "Always give your dimensions in quantitative terms if possible. Go on."
"There are a couple of waterproof sheets," said I. "I don't see quite what they can have been used for."
"Never mind their use," said Thorndyke. "Note the fact that they are here."
"I have," said I; "and that seems to complete the list with the exception of the straw in which I suppose the gas cylinders were packed. There is a large quantity of that, but not more than would seem necessary for the purpose. And that seems to complete the inventory, and, I may say, that none of these things conveys any suggestion whatever to my mind."
"Probably not," said Thorndyke, "and it is quite possible that none of these things has any particular significance at all. But as they are the only facts offered us, we must make the best of them. There is one other cellar that we have not yet looked into, I think."
We came out, and, walking along the passage, came to another door which stood slightly ajar. Thorndyke opened it, and, throwing in the light of his lamp, revealed a considerable stack of long iron gas bottles, and one or two packing-cases similar to the one I had already seen. "I presume," said he, "that these are full cylinders; the store from which our friend got his supply, but we may as well make sure."
He ran back into the adjoining cellar, and returned with the spanner, with which he proceeded to turn the cock of one of the topmost cylinders; upon which a loud hiss and a thin, snowy cloud showed that his surmise was correct.
He had just closed the cock and stepped out into the passage to take back the spanner, when I saw him stop suddenly as if listening. And then he sniffed once or twice. "What is it?" asked Jervis; but Thorndyke, without replying, ran quickly along the passage and up the steps, and I heard him trying the door at
