“Mixed up with the traces of a good many others,” I remarked. “True,” he admitted. “But that would not affect the value of a positive trace of a particular individual. Supposing, for instance, that Godfrey Herrington were known to have dyed hair; and suppose that one or more dyed male hairs were found in the dust from the floor of the room. That would establish a probability that he had been in that room, and also that he was the person who had struggled with the deceased.” “Yes, I see that,” said I. “Perhaps I ought to have collected some of the dust. But it isn’t too late now, as Bidwell has locked up the chambers. Meanwhile, let me present you with Badger’s clues. They came off the floor.” I searched in my pocket and produced the paper packet, the existence of which I had forgotten, and having opened it, offered it to him with an ironical bow. He looked gravely at the little collection, and, disregarding the pin and the match, picked out the third object and examined it curiously. “That is the alleged boot-lace end,” he remarked. “It doesn’t do much credit to Badger’s powers of observation. It is as unlike leather as it could well be.” “Yes,” I agreed, “it is obviously whalebone or vulcanite.” “It isn’t vulcanite,” said he, looking closely at the broken end and getting out his pocket lens for a more minute inspection. “What do you suppose it is?” I asked, my curiosity stimulated by the evident interest with which he was examining the object. “We needn’t suppose,” he replied. “I fancy that if we get Polton to make a cross section of it, the microscope will tell us what it is. I will take it up to him now.” As he went out and I heard him ascending to the laboratory where our assistant, Polton, was at work, I was conscious of a feeling of vexation and a sense of failure. It was always thus. I had treated this fragment with the same levity as had the inspector, just dropping it into my pocket and forgetting it. Probably the thing was of no interest or importance; but whether it was or not, Thorndyke would not be satisfied until he knew for certain what it was. And that habit of examining everything, of letting nothing pass without the closest scrutiny, was one of the great secrets of his success as an investigator. When he came down again I re-opened the subject. “It has occurred to me,” I said, “that it might be as well for us to have a look at that room. My inspection was rather perfunctory, as Badger was there.” “I have just been thinking the same,” he replied. “If Godfrey is not the man, and the police are left stranded, Bidwell will look to us to take up the inquiry, and by that time the room may have been disturbed. I think we will get the key from Bidwell to-morrow morning and make a thorough examination. And we may as well adopt Badger’s excellent suggestion respecting the dust. I will instruct Polton to come over with us and bring a full-sized vacuum-cleaner, and we can go over what he collects at our leisure.”