“He’s terribly worried, of course. We thought at first that his secretary was the man, but we can’t find the slightest grounds for suspicion against him, and Winthrop’s had him in his employ for years. It’s the greatest mystery I’ve struck yet. We’ve been working to dis-cover the betrayer for months, and we’re no nearer a solution now than we were when we began. And still it goes on. Take the affair of the negotiations with Carmania. They leaked into Russia, we know. Or take the case of the submarines. Those plans weren’t stolen, they were just copied. The only person, seemingly, who could have done it was Winthrop. He alone knows the secret of Caryu’s safe. The plans were with Caryu for three days. All the rest of the time they were with Tassel, and they never left him for a moment. The thing must have been done during those three days that they were in Caryu’s safe, because before that date they were incomplete, and dates show that they can’t have been copied after they were returned to Fothermere. Now, having whittled the date down to three days, how much nearer the solution are we? Of course, everything points to Winthrop.”

“Or Caryu,” said Linckes quietly.

“My good youth, are you seriously accusing Mr. Caryu? Even supposing that he is the man we’re after—which he isn’t—would he have copied the plans while they were in his house? He’s not a fool, you know.”

“Where was he during those three days?”

“At home. Winthrop went round to his house, and together they examined the plans. That was on the first day, and Winthrop left the house soon after nine in the evening. Shortly after he had gone Caryu put the plans into his safe. He had them with him next day at the War Office, and put them into the safe when he came home. Not even his secretary knew of their existence. They were returned to Tassel on the following afternoon.”

Linckes’ forehead wrinkled in perplexity. “When did Johnson see them?”

“Before. He worked with Tassel, you see.”

“Um! And where did Sir Charles Winthrop go when he left Caryu’s house that night?”

“He went straight down to his place in the country—Millbank. Took Max Lawson with him. He was there for the rest of the week, with a small house-party. That wipes him off the list.”

“What sort of a man is he?” Linckes asked. “All I know is that he’s fairly young, very clever, and good-looking, rich, and an orphan.”

“He’s an awfully decent chap. Everybody likes him. Son of old Mortimer Winthrop. the railwayman. Mortimer separated from his wife when Charles was a kid. You know Charles’ history. She went abroad with the other child, I believe, and Mortimer kept Charles. Did awfully well in the Secret Service during the war, and rose like a rocket. He’ll be a big man before long, if this awful business is cleared up. Of course, he feels pretty badly about it. Means he’ll perhaps have to resign his post.”