If his name had cropped up the fat would have been in the fire. Our ingenuous government still seem to be under the illusion that they can scrape through without going to war, and to bring a charge of that nature against a prominent Hun diplomat without cast-iron evidence to back it up—well, the mere suggestion would be sufficient to throw the whole Foreign Office into hysterics.”

“But surely something ought to be done, sir? If they can get hold of one set of plans—”

“They might be tempted to repeat the experiment? Exactly. You have hit upon the very point which is at present giving my particular department an outsize in headaches. I can assure you that the Mayflower Club and its proprietor are a subject of the deepest interest to us.”

“Who is this fellow Mark Craig, sir? Is that his real name?”

“So far as I know. He is an Irish American who has spent most of his early life in the States. He came over here six years ago with a certain amount of cash, and very soon afterwards he launched out in his present racket in Grosvenor Street. He must be a clever devil—I’ll give him credit for that. The place was a success from the first, and although the police have been keeping an eye on it they have never caught him out in any actual infringement of the law. All the same, they are convinced that he’s a bad lot, and that when he sees the chance he has no objection to doing a bit of blackmailing. My own belief is that he’s a Nazi agent, and that he is being subsidised from Berlin.”

“Isn’t that good enough, sir? Can’t you have him arrested and locked up?”

“Might be arranged, but it would only mean that the work would be handed over to somebody else. As it is, we at least have the advantage of knowing where the mischief is likely to be hatched. Unfortunately, if the thing is as well organised as it appears to be, Mr. Craig and his friends are probably pretty well posted with regard to our own activities. I have several first-class men working under my direction, but I wouldn’t mind betting a hundred pounds that every one of them is either known or suspected. When it comes to spying the Hun does his job thoroughly.”

Owen looked straight into the shrewd grey eyes that were fixed steadily on his own. “I take it that you have some special reason for telling me all this, sir.”

“Naturally.” The other leaned back in his chair. “I think you might be useful to me, Bradwell. You are being given two months’ sick leave, and if you feel like putting your services at my disposal for that period I am quite prepared to accept your offer. The whole arrangement, of course, would be strictly unofficial.”

“Sounds all right to me, sir. I don’t imagine I should be much good as a detective, though.”

“Possibly not. Still, Carmichael is a fairly sound judge of character, and if his statements about you are correct, I believe we are justified in making the experiment.” Greystoke gave another of his oddly attractive smiles. “After all, there is a certain amount of scientific evidence in favour of such a proceeding. According to Edridge-Green, who is the principal authority on the subject, people who suffer from colour-blindness are generally above the average in intelligence. Perhaps that is why it is so rare amongst our Cabinet Ministers.”

Owen laughed.

“Well, what have you got to say about it? Does the prospect appeal to you?”

“I should be delighted to have a try, sir.”

“Excellent. I had better explain what I have in my mind. As I told you a moment ago, we are keeping a close eye on the Mayflower Club, and also on its distinguished clientele. Two of my staff are actually members, but since it’s more than likely that our friend Mr. Craig is well aware of the fact, I should imagine that any dirty work he may be arranging to pull off will probably be discussed somewhere else. The most likely place I can think of would be Otter’s Holt, the island he owns down at Thames Ferry. Do you happen to know it by any chance?”

“I know where it is, sir.