“You mean,” said Carden’s voice, “that you have actually solved the proposition?”

“It has been a difficult proposition, Mr. Carden; I will not deny that it has taxed our resources to the uttermost.  Over a thousand people, first and last, have been employed on this case.  It has been a slow and tedious affair, Mr. Carden—­tedious for us all.  We seldom have a case continue as long as this has; it is a year ago to-day since you placed the matter in our hands. . . .  What?  Well, without committing myself, I think that I may venture to express a carefully qualified opinion that the solution of the case is probably practically in the way of being almost accomplished! . . .  Yes, I shall expect you in half an hour.  Good-by!”

The Tracer of Lost Persons’ eyes were twinkling as he hung up the receiver and turned in his revolving chair to meet the pretty young woman who had entered in response to his ring.

“The Carden case, if you please, Miss Smith,” he said, smiling to himself.

The young woman also smiled; the Carden case had become a classic in the office.  Nobody except Mr. Keen had believed that the case could ever be solved.

“Safe-deposit box 108923!” said Miss Smith softly, pressing a speaking tube to her red lips.  In a few moments there came a hissing thud from the pneumatic tube; Miss Smith unlocked it and extracted a smooth, steel cylinder.

“The combination for that cylinder is A-4-44-11-X,” observed the Tracer, consulting a cipher code, “which, translated,” he added, “gives us the setting combination, One, D, R-R,-J-’24.”

Miss Smith turned the movable disks at the end of the cylinder until the required combination appeared.  Then she unscrewed the cylinder head and dumped out the documents in the famous Carden case.

“As Mr. Carden will be here in half an hour or so I think we had better run over the case briefly,” nodded the Tracer, leaning back in his chair and composing himself to listen.  “Begin with my preliminary memorandum, Miss Smith.”

“Case 108923,” began the girl.  Then she read the date, Carden’s full name, Victor Carden, a terse biography of the same gentleman, and added:  “Case accepted.  Contingent fee, $5,000.”

“Quite so,” said Mr. Keen; “now, run through the minutes of the first interview.”

And Miss Smith unrolled a typewritten scroll and read: 

“Victor Carden, Esquire, the well-known artist, called this evening at 6.30.  Tall, well-bred, good appearance, very handsome; very much embarrassed.  Questioned by Mr. Keen he turned pink, and looked timidly at the stenographer (Miss Colt).  Asked if he might not see Mr. Keen alone, Miss Colt retired.  Mr. Keen set the recording phonograph in motion by dropping his elbow on his desk.”

A brief resume of the cylinder records followed: