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?
Anyway, here were certain facts--and they had to be reckoned with.
Kitely was murdered about a quarter-past nine o'clock.