When Bent had gone away to the town, Brereton lighted a cigar, stretched himself in an easy chair in front of a warm fire in his host's smoking-room, and tried to think clearly. He had said to Bent all that was in his mind about Harborough and about Miss Pett--but he had said nothing, had been determined to say nothing, about a curious thought, an unformed, vague suspicion which was there. It was that as yet formless suspicion which occupied all his mental powers now--he put Harborough and Miss Pett clean away from him. And as he sat there, he asked himself first of all--why had this curious doubt about two apparently highly-respectable men of this little, out-of-the-world town come into his mind? He traced it back to its first source--Cotherstone. Brereton was a close observer of men; it was his natural instinct to observe, and he was always giving it a further training and development. He had felt certain as he sat at supper with him, the night before, that Cotherstone had something in his thoughts which was not of his guests, his daughter, or himself. His whole behaviour suggested pre-occupation, occasional absent-mindedness: once or twice he obviously did not hear the remarks which were addressed to him. He had certainly betrayed some curious sort of confusion when Kitely's name was mentioned. And he had manifested great astonishment, been much upset, when Garthwaite came in with the news of Kitely's death. Now here came in what Brereton felt to be the all-important, the critical point of this, his first attempt to think things out. He was not at all sure that Cotherstone's astonishment on hearing Garthwaite's announcement was not feigned, was not a piece of pure acting. Why? He smiled cynically as he answered his own question. The answer was--_Because when Cotherstone, Garthwaite, Bent, and Brereton set out from Cotherstone's house to look at the dead man's body, Cotherstone led the way straight to it_. How did Cotherstone know exactly where, in that half-mile of wooded hill-side, the murder had been committed of which he had only heard five minutes before? Yet, he led them all to within a few yards of the dead man, until he suddenly checked himself, thrust the lantern into Garthwaite's hands and said that of course he didn't know where the body was! Now might not that really mean, when fully analyzed, that even if Cotherstone did not kill Kitely himself during the full hour in which he was absent from his house he knew that Kitely had been killed, and where--and possibly by whom?