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——”

“Just so. The consequence is that you get a very unsatisfactory affair that has no special interest to an amateur and is only baffling because it is—well——”

“Well, baffling?”

“Exactly, Max. Your would-be jest has discovered the proverbial truth. I need hardly tell you that it is only the insoluble that is finally baffling and this is very probably insoluble. You remember the awful smash on the Central and Suburban at Knight’s Cross Station a few weeks ago?”

“Yes,” replied Carrados, with interest. “I read the whole ghastly details at the time.”

“You read?” exclaimed his friend suspiciously.

“I still use the familiar phrases,” explained Carrados, with a smile. “As a matter of fact, my secretary reads to me. I mark what I want to hear and when he comes at ten o’clock we clear off the morning papers in no time.”

“And how do you know what to mark?” demanded Mr Carlyle cunningly.

Carrados’s right hand, lying idly on the table, moved to a newspaper near. He ran his finger along a column heading, his eyes still turned towards his visitor.

“‘The Money Market. Continued from page 2. British Railways,’” he announced.

“Extraordinary,” murmured Carlyle.

“Not very,” said Carrados. “If someone dipped a stick in treacle and wrote ‘Rats’ across a marble slab you would probably be able to distinguish what was there, blindfold.”

“Probably,” admitted Mr Carlyle. “At all events we will not test the experiment.”

“The difference to you of treacle on a marble background is scarcely greater than that of printers’ ink on newspaper to me. But anything smaller than pica I do not read with comfort, and below long primer I cannot read at all. Hence the secretary. Now the accident, Louis.”

“The accident: well, you remember all about that. An ordinary Central and Suburban passenger train, non-stop at Knight’s Cross, ran past the signal and crashed into a crowded electric train that was just beginning to move out. It was like sending a garden roller down a row of handlights. Two carriages of the electric train were flattened out of existence; the next two were broken up. For the first time on an English railway there was a good stand-up smash between a heavy steam-engine and a train of light cars, and it was ‘bad for the coo.’”

“Twenty-seven killed, forty something injured, eight died since,” commented Carrados.

“That was bad for the Co.,” said Carlyle. “Well, the main fact was plain enough. The heavy train was in the wrong. But was the engine-driver responsible? He claimed, and he claimed vehemently from the first and he never varied one iota, that he had a ‘clear’ signal—that is to say, the green light, it being dark. The signalman concerned was equally dogged that he never pulled off the signal—that it was at ‘danger’ when the accident happened and that it had been for five minutes before. Obviously, they could not both be right.”

“Why, Louis?” asked Mr Carrados smoothly.

“The signal must either have been up or down—red or green.”

“Did you ever notice the signals on the Great Northern Railway, Louis?”

“Not particularly. Why?”

“One winterly day, about the year when you and I were concerned in being born, the engine-driver of a Scotch express received the ‘clear’ from a signal near a little Huntingdon station called Abbots Ripton. He went on and crashed into a goods train and into the thick of the smash a down express mowed its way. Thirteen killed and the usual tale of injured. He was positive that the signal gave him a ‘clear’; the signalman was equally confident that he had never pulled it off the ‘danger.’ Both were right, and yet the signal was in working order. As I said, it was a winterly day; it had been snowing hard and the snow froze and accumulated on the upper edge of the signal arm until its weight bore it down. That is a fact that no fiction writer dare have invented, but to this day every signal on the Great Northern pivots from the centre of the arm instead of from the end, in memory of that snowstorm.”

“That came out at the inquest, I presume?” said Mr Carlyle. “We have had the Board of Trade inquiry and the inquest here and no explanation is forthcoming. Everything was in perfect order. It rests between the word of the signalman and the word of the engine-driver—not a jot of direct evidence either way. Which is right?”

“That is what you are going to find out, Louis?” suggested Carrados.

“It is what I am being paid for finding out,” admitted Mr Carlyle frankly. “But so far we are just where the inquest left it, and, between ourselves, I candidly can’t see an inch in front of my face in the matter.”

“Nor can I,” said the blind man, with a rather wry smile.