"Very interesting," admitted Mr Carlyle; "but at the risk of seeming obtuse"--his manner had become delicately chastened--"I must say that I fail to trace the inevitable connexion between Nina Brun and this particular forgery--assuming that it is a forgery." "Set your mind at rest about that, Louis," replied Carrados. "It is a forgery, and it is a forgery that none but Pietro Stelli could have achieved. That is the essential connexion. Of course, there are accessories. A private detective coming urgently to see me with a notable tetradrachm in his pocket, which he announces to be the clue to a remarkable fraud--well, really, Louis, one scarcely needs to be blind to see through that." "And Lord Seastoke? I suppose you happened to discover that Nina Brun had gone there?" "No, I cannot claim to have discovered that, or I should certainly have warned him at once when I found out--only recently--about the gang. As a matter of fact, the last information I had of Lord Seastoke was a line in yesterday's _Morning Post_ to the effect that he was still at Cairo. But many of these pieces----" He brushed his finger almost lovingly across the vivid chariot race that embellished the reverse of the coin, and broke off to remark: "You really ought to take up the subject, Louis. You have no idea how useful it might prove to you some day." "I really think I must," replied Carlyle grimly. "Two hundred and fifty pounds the original of this cost, I believe." "Cheap, too; it would make five hundred pounds in New York to-day. As I was saying, many are literally unique. This gem by Kimon is--here is his signature, you see; Peter is particularly good at lettering--and as I handled the genuine tetradrachm about two years ago, when Lord Seastoke exhibited it at a meeting of our society in Albemarle Street, there is nothing at all wonderful in my being able to fix the locale of your mystery. Indeed, I feel that I ought to apologize for it all being so simple." "I think," remarked Mr Carlyle, critically examining the loose threads on his left boot, "that the apology on that head would be more appropriate from me." THE KNIGHT'S CROSS SIGNAL PROBLEM "Louis," exclaimed Mr Carrados, with the air of genial gaiety that Carlyle had found so incongruous to his conception of a blind man, "you have a mystery somewhere about you! I know it by your step." Nearly a month had passed since the incident of the false Dionysius had led to the two men meeting. It was now December. Whatever Mr Carlyle's step might indicate to the inner eye it betokened to the casual observer the manner of a crisp, alert, self-possessed man of business. Carlyle, in truth, betrayed nothing of the pessimism and despondency that had marked him on the earlier occasion. "You have only yourself to thank that it is a very poor one," he retorted. "If you hadn't held me to a hasty promise----" "To give me an option on the next case that baffled you, no matter what it was----"