The superintendent was soon speeding two steps at a time.

“The Captain is back, Mr. Shirley,” he exclaimed.  “He’s in the private office on a couch.”

“Good, then we’ll take my friend right to him.”

The stranger was beginning to evidence uneasiness, and he turned questioningly to his conductor, with a growing frown.

“Say, what are you leading me into, Chief?”

Shirley said nothing but strode to the rear of the floor, through the door of Captain Cronin’s sanctum.  The old detective was covered with a steamer shawl, as he stretched out on a davenport.  The young man observed the photographs around the room,—­an enormous collection of double-portraits of profile and front face views—­the advertized crooks for whom Cronin had his nets spread in a dozen cases.  The handcuffs on the desk, the measuring stand, the Bertillon instruments on the table, all these aroused his suspicions instantly.

He whirled about, angrily.

Shirley smiled in his face.  Then he addressed the surprised Captain Cronin.

“Here is our little telephone expert who arranged the wires for Warren and his gang, Captain.  You are welcome to add him to your growing collection of prisoners.”

For answer the young man whipped out a revolver and fired point-blank at the criminologist.  His was a ready trigger finger.  But he was no swifter than the convalescent detective on the couch, who had swung a six shooter from a mysterious fold of the steamer blanket, and planted a bullet into the man’s shoulder from the rear.

As the smoke cleared away, Shirley straightened up from the crouching position on the floor which had saved him from the assassin, and dragged the wounded criminal to his feet.  The handcuffs clicked about his wrists before the young man had grasped the entire situation.  Cleary and three others of the private force were in the room.

“I’ve got to hurry along now, Captain.  Just let him know that his Chief is captured and the sooner he turns State’s evidence the better it will be for him.  The District Attorney might make it lighter, if he helps.  I’ll be back this evening if I can.”  And Shirley hurried away, leaving much surprise and bewilderment in every mind.

Cronin was equal to the task of picking up the threads, and under his sarcasm, and Cleary’s rough arguments, the prisoner admitted some interesting matters about the mysterious employer whose face he had never seen.  But Shirley’s task was far from completed.

CHAPTER XX

A DOUBLE ON THE TRAIL

Shirley walked up to the Hotel California, at the door of which he met Warren and Taylor just leaving.  They looked somewhat embarrassed but his manner was cordiality itself.

“Sorry you are going.  I was just stepping up to see Miss Marigold.  Won’t you come back?”

His invitation was refused.  Then Shirley urged Warren to be his guest at the club for dinner that evening.  This was accepted with a surprising alacrity.  So, he left them, and was soon talking with Helene.