"It might belong to anyone. I've seen dozens like it. I used to have one myself, if it comes to that. Anyone could have dropped it."
"No idea who, sir?"
"No, none at all," said White, looking him in the eye.
"Well, that's very disappointing. Mind if I ask your son if he happens to know anything about it?"
"Good Lord, you don't suppose my son had anything to do with Carter's death, do you? You're wasting your time! He'd got no interest in Carter whatsoever."
"Still, I don't know why you should object to my asking him if he's seen the knife before," said the Inspector.
White got up. "Object! I don't care a damn how you choose to waste your time. I'll call my son."
Alan, stridently summoned, lounged into the study a moment or two later. From the defensive expression on his face, the Inspector judged that he expected to be violently taxed with having betrayed his parent. He made haste to dispel this fear by holding out the pocketknife. "Good afternoon, sir. Ever seen that before?"
Alan looked rather relieved, and took the knife. "Where did you find it?"
"Do you recognise it, sir?"