“I’m not surprised that nothing seems to have been disturbed,” he murmured. “The men who were smart enough to get in here and put Anderton to death by the crossed needles would not be likely to leave obvious traces of their presence. Well, I’ll look into that later. First of all, let’s see whom poor Anderton was writing to when he was killed.” Passing over the blank sheet, with only the date line, which lay immediately in front of the chair, Nick picked up another letter, sealed, addressed, and stamped. Evidently it had been finished just before the deceased had begun the other. “‘Matthew Bentham, esquire,’” read Carter, with the envelope in his hand. “Ah! That’s the scientist and Orientalist. I did not know that he was a friend of Anderton’s. But it is quite natural that men having the same interests should be acquainted. I see Bentham lives in Brooklyn. I’ll take down that address.” It was in an avenue near Prospect Park, and Nick carefully copied the superscription into his notebook. Then he opened the door of the study and called down the staircase to the butler Ruggins. “Ask Mr. Chickering Carter to come here,” requested Nick. In a moment Chick was bounding up the stairs. His chief handed him the letter addressed to Bentham. “Mail this at once, Chick. You’d better take it to the nearest branch post office. I wouldn’t trust it to a mail box outside. I want to make sure it will be delivered in the morning.” When Chick had departed with the letter, Nick again closed and locked the door and began his investigations in earnest. Turning on all the electric lights, and with his flash lamp in his hand, he examined the floor, in the hope of finding marks of feet on the polished floor or the costly rugs that would give him a clew. “Ah, here is something!” he exclaimed, in a low tone. “But it only confirms what I already knew--that a Chinaman killed Anderton. Still, I did not know until now that the fellow wore the regular Chinese felt-soled slippers. This proves it, however.” He was holding the light of his flash upon a certain spot on one of the dark-green rugs, and he could trace the shape of a broad foot--perfectly flat, without any gap for the instep that would be made by an ordinary heeled shoe--outlined in a gray dust. The dust was very indistinct, and if the detective had not had such a strong light to help him, he might have overlooked it altogether. “Wood ash, I think.” He wetted a finger, pressed it into the gray footprint, and put the finger into his mouth. It was salty. “That’s what it is,” he muttered. “Ah, of course! From the fireplace. Anderton always would have a wood fire burning in his room, no matter what the weather might be.” Indeed, there was a large, handsome fireplace, wide and high, with two great brass andirons, or firedogs, at one side of the spacious room. On the andirons were two logs of wood, half burned through, and the gray ash from them was scattered over the tiled hearth.