“That,” said Thorndyke, “is a common delusion. As a matter of fact they would have quite the opposite effect. You have only to hold an inverted tumbler over a burning candle to realize, from the moisture which immediately condenses on the inside of the tumbler, that the candle, as it burns, gives off quite a considerable volume of steam. But of course, the bulk of the moisture which has caused the paper to peel in this room came from the man’s own breath. However, we didn’t come here for debating purposes. Let us complete our preliminary tour, and when we have seen the whole house we can each make such more detailed inspection as seems necessary for our particular purposes.”
We accordingly resumed our perambulation (but I noticed that Thorndyke deposited his attaché case in Monkhouse’s room with the evident intention of returning thither), both of us looking about narrowly: Thorndyke, no doubt, in search of the mysterious “traces” of which he had spoken, and I with an inquisitive endeavour to ascertain what kind of objects or appearances he regarded as “traces.”
We had not gone very far before we encountered an object that even I was able to recognize as significant. It was in a corner of the long corridor that we came upon a little heap of rubbish that had been swept up out of the way; and at the very moment when Thorndyke stopped short with his eyes fixed on it, I saw the object—a little wisp of knitting-wool of the well-remembered green colour. Thorndyke picked it up, and, having exhibited it to me, produced from his letter-case a little envelope such as seedsmen use, in which he put the treasure trove, and as he uncapped his fountain pen, he looked up and down the corridor.
“Which is the nearest room to this spot?” he asked.
“Madeline’s,” I replied. “That is the door of her bedroom, on the right. But all the principal bedrooms are on this floor and Barbara’s boudoir as well. This heap of rubbish is probably the sweepings from all the rooms.”
“That is what it looks like,” he agreed as he wrote the particulars on the envelope and slipped the latter in his letter-case. “You notice that there are some other trifles in this heap—some broken glass, for instance. But I will go through it when we have finished our tour, though I may as well take this now.”
As he spoke, he stooped and picked up a short piece of rather irregularly shaped glass rod with a swollen, rounded end.
“What is it?” I asked.
“It is a portion of a small glass pestle and it belongs to one of those little glass mortars such as chemists use in rubbing up powders into solutions or suspensions. You had better not touch it, though it has probably been handled pretty freely. But I shall test it on the chance of discovering what it was last used for.”
He put it away carefully in another seed-envelope and then looked down thoughtfully at the miniature dust-heap; but he made no further investigations at the moment and we resumed the perambulation, I placing the identification card on the mantelpiece of each room while he looked sharply about him, opening all cupboards and receptacles and peering into their, usually empty, interiors.