"You don't believe he must have anticipated that?" asked Evelyn.
"Quite seriously, I don't think he did," said H.M. "Give the devil fair play. For see what he did. To show that an outsider must have been there, he manufactured evidence (it was bad evidence, but it had to be obvious stuff) in order to show the sash window had been burgled."
"Hold on!" said Stone. "This won't do! You can't have it both ways. You say he got in and manufactured the evidence. All right. You said earlier this evening that the catch on that window was broken from inside, and the scratches made from inside. But you also said that no other window or door in the house showed any sign of being tampered with! In that case, how in the name of Judas did Charters get in to make those marks on the inside? He couldn't have got in."
H.M. again spoke with a sort of lowering mirth.
"Oh yes, son. Anybody could have got in. Anybody could have got in, and left no betrayin' sign on the French window. Anybody, that is, who had at hand a full kit of the finest and most modern burglar's tools. And Charters was the only one who had a kit like that. He lent it to Ken the following night."
After a pause, H.M. went on:
"I tried to show it to you; that was why I hammered the point about that sash-window; and, burn me, Charters almost came out and admitted the truth when he was defendin' the Antrims. He pointed out how both of 'em could have been tellin' the truth when I pressed him. I told you the little things were important. He broke that window from the inside, so it would make little noise; he broke it with a big claspknife — the same clasp-knife, I rather think, that he made you a present of when I sent you to do some burglin' yourself at the Cabot Hotel in Bristol.
"But there was the trouble. Y'see, when he sneaked out that night, Serpos saw him.
"Serpos has admitted that much to me. It supplies the explanation to the last nightmare in the business. I mean the telephone-call to the Cabot Hotel at one-thirty, when someone whispered: `This is L. speaking. Would you like to know the truth about the money?' And then the laugh. It was Serpos speaking for blackmail. It was Serpos speaking — with a hint. It was Serpos speaking — with Charters standin' right beside him. If you got any memories, you'll recall that Antrim looked down over the banisters and saw Serpos loungin' against the edge of the stairs. Uh-huh. But there was somebody else there, too. Somebody bidden from Antrim under the protection of the stairs. Somebody standin' there and sweatin'. Charters."
"Yes," I said, "but how the devil did Serpos come to call up Keppel? Where was the blackmail in that? What made him think of that?"