The more he considered the affair in all its bearings, the more conscious he became of the soundness of the advice he had given to Cheyne, and which in his turn he had received from his chief. Unquestionably in the tracing lay the solution he required, and once again he racked his brains to see if he could not by any means devise a way to read its message. On this point he concentrated, going over and over again everything he had learned about it. For perhaps an hour he remained motionless in his chair, while the smoke from his cigar curled up and slowly dissolved into the blue haze with which the room was becoming obscured. And then suddenly he sat up and with a dawning, tremulous eagerness considered an idea which had just leaped into his mind. He had suddenly remembered a statement made by Cheyne when he was giving his first rather incoherent account of his adventures. The young man said that it had been arranged between himself and Joan Merrill that if either were lucky enough to get the tracing into his or her possession, the first thing he or she would do would be to photograph it. Now, in juxtaposition with that statement, French recalled the facts, first, that Joan must have reached her flat on the night of her abduction at least several minutes before Blessington and Sime arrived with their car; and secondly, that during those minutes she had the tracing with her—the genuine tracing, as there was every reason to believe. _Had Joan photographed it?_ French was overwhelmed with amazement and chagrin at his failure to think of this point before, nor could he acquit Cheyne of a like astounding stupidity. For himself he felt there was no excuse whatever. He had even specially noticed the girl’s camera and the flashlight apparatus which she used for her architectural details when he was searching her rooms, but he had then, and since then up till this moment, entirely and completely forgotten the arrangement made between the partners. Late as it was, French decided to go then and there to ascertain the point. The key of Joan’s flat was at the Yard, and twenty minutes later he had obtained it and was in a taxi bowling towards Horne Terrace. He kept the vehicle while he ran up the ten flights to No. 12 and secured the camera. Then hastening down, he was driven back to the Yard. By a piece of good luck he found a photographer who had been delayed by other important work, and him he pressed into the service forthwith. With some grumbling the man returned to his dark room. French, too eager to await his report, accompanying him. A few moments sufficed to settle the question. The camera contained a roll of films of which the first seven had been exposed, and a short immersion in the developer showed that numbers 5, 6, and 7 bore the hoped for impress.