“I know, sir. I don’t expect the thief to attempt it. I want you to tell Sir Charles, when you see him tomorrow, that you have made one or two suggestions on the plans, and are sending them by your secretary to his house for him to see.”

Caryu reddened.

“What are you driving at?” he asked levelly. “What do you mean?”

“Just that, sir. I think Mr. Fortescue carries documents to Sir Charles’ house fairly often? Minor documents, I mean.”

“Certainly. But I do not understand—”

“I know, sir. I want you to give Mr. Fortescue a package containing blank sheets. Keep the plans in your safe.”

Caryu drew himself up. “Linckes, you must please explain yourself. I don’t know what crack-brained notion you have got into your head, but if you are insinuating that Sir Charles is the criminal, I may as well tell you that it is an impertinent and foolish suggestion.”

“I’m not insinuating anything, sir. I can’t even tell you who I suspect. But I do beg of you to just do as I ask without mentioning my name. It can’t do any harm, and I believe it’ll enable me to find the man who’s betraying us all.”

Caryu’s face softened a little.

“You think that whoever is doing it will try to intercept Fortescue on his way to Winthrop’s house? It is rather improbable, isn’t it? He has only a few yards to go.”

“That’s just what I’m counting on, sir. It’s too short a distance for him to take a taxi. He doesn’t, I know, for I’ve often been with Winthrop when he has come over with a letter for you, or, as I said, some minor document.”

Caryu was silent for a moment. He looked Linckes over, frowning.

“And when Fortescue comes to Winthrop and gives him a package of blank sheets,” he said sarcastically, “what am I to say to Winthrop? You don’t seem to understand that if that happens my action in sending blank sheets amounts to a very serious insult.”

“No, sir. If Fortescue does arrive, unmolested, and with the blank sheets, you can explain why it was done. You don’t suspect Sir Charles. I haven’t said that I do. It’s quite simple.”

Caryu smiled faintly. “Very well. I will tell Winthrop that among other things I am sending him the plan of the new ’plane. Are you satisfied?”

“Yes, sir. Thank you!”

Linckes rose and prepared to depart.

“What happens if Fortescue is sandbagged?” inquired Caryu. “What will he think of your little plot?”

“Not much chance of that, sir,” Linckes grinned. “From Park Lane to Arlington Street isn’t a far cry, and it’s never exactly deserted. But don’t tell Fortescue anything, will you? Not even that you are supposed to be sending plans. Send him off at the usual time.”

“‘The usual time’ covers a wide margin,” remarked Caryu. “I shall send him at about six in the evening. That is the most usual time.”

“Then tell Winthrop, sir, casually. And thanks awfully!”