“That was on Tuesday,” said Landis. “Have you done any shooting up there since Tuesday, Mr. Harrison?”
Joel shook his head.
“No. It was not necessary. The weather has been fine. Of course one prefers butt-shooting for the added hazard due to windage in the open.”
“All right, Mr. Harrison. We’re enormously obliged to you. Now I suggest you go back to your bed and your book. If we need anything more, we’ll see you tomorrow.”
Joel rose obediently and started out of the room, paused to bow a courteous good night and vanished.
At precisely that same moment, Thorpe came hurrying along the library to Landis.
“Look here, Lieutenant,” he exclaimed. “This is an amazing thing! While I was taking those photographs, somebody has wiped the blurred finger-prints off the door!”
Landis leapt from his chair and strode to the end of the library. Finger-prints, picked out with white chalk, were plainly visible on the knob of the half-closed door. But the woodwork was smooth and unmarked.
He hurried into the hall to look at the other side. Door-knob and door-edge bore no traces of chalk. He looked swiftly about the deserted hall. At the end of it nearest the swinging doors and the butler’s pantry, something tiny and crumpled and white caught his eye. He ran to it and picked it up, carrying it back to Bernard in the library. It was a woman’s lace handkerchief. Landis explained swiftly where he had found it. He carried it to the desk lamp where they studied it together. The crumpled folds were ridged with white chalk. In one corner they found the initials: “I. H.”