Their feet sank noiselessly into the thick carpet of the stairs as they moved towards the death-chamber. From an open doorway near the landing a flood of light issued. "Very handy for any one to get away," commented Foyle. "The stairs lead direct to the hall, and there are only two rooms to pass. This carpet would deaden footsteps too." They entered softly. Some one had turned all the lights on in the room, and it was bathed in brilliance. A dying fire flickered in the grate; bookcases lined the red-papered walls, which were broken here and there by curios and sporting trophies gathered from many countries. There were a few etchings, which had evidently been chosen with the skill of a connoisseur. Parallel with the window was a desk, scrupulously tidy. Half a dozen chairs were scattered about, and in a recess was a couch, over which the angular frock-coated figure of Professor Harding was bent. He looked up as the two men approached. "It's clearly murder," he said. "He was probably killed between ten and eleven--stabbed through the heart. Curious weapon used too--look!" He moved aside and for the first time Foyle got a view of the body. Robert Grell lay sprawled awkwardly on the couch, his face turned towards the wall, one leg trailing on the floor. A dark crimson stain soiled the white surface of his shirt, and one side of his dinner jacket was wringing wet. The dagger still remained in the wound, and it was that riveted Foyle's attention. He stepped back quickly to one of the men at the door. "Send Mr. Grant to me," he ordered. Returning to the body, he gently withdrew the knife, handling it with the most delicate care. "I've never seen anything like this before," he said. "Queer thing, isn't it?" It was a sheath knife with a blade of finely tempered steel about three inches long and as sharp as a razor. Its abnormality lay in a hilt of smooth white ivory set horizontally and not vertically to the blade, as is a rule with most knives. Foyle carried it in the palm of his hand nearer to the light and squinted at it from various angles. One at least of the observers guessed his purpose. But the detective seemed dissatisfied. "Can't see anything," he grumbled peevishly. "Ah, there you are, Grant. I want to see whether we can make anything of this. Let me have a little graphite, will you?" The finger-print expert took an envelope from his pocket and handed it to the superintendent. From it Foyle scattered fine black powder on the hilt. A little cry of satisfaction came from his lips as he blew the stuff away in a little dark cloud. Those in the room crowded around. Outlined in black against the white surface of the ivory were four finger-prints. The two centre ones were sharp and distinct, the outside prints were fainter and more blurred. "By Jove, that's good!" exclaimed the professor.