The criminologist picked his way through the swarming vehicles which swung up and down Broadway, across to Seventh Avenue, where he turned into a plumber's shop. This fellow had handled small jobs on Shirley's extensive real estate holdings, and he was naturally delighted to do a favor in the hope of obtaining new work.

“Mike, I want to borrow an old pair of overalls, a jumper and one of those blue caps hanging up on your wall. And I need some plumbers' tools, as well, for a little joke I am to play on one of my friends.”

The workman was astounded at such a request from his rich client, but nodded willingly. The dirtiest of the clothes answered Shirley's requirements and with soot rubbed over his face and hands, his hair disarranged, he satisfied his artistic craving for detail. He was transformed into a typical leadpipe brigand. Hanging his own garments in the closet, after transferring his automatic revolver into the pocket of the jeans, he started out, carrying the furnace pot, and looking like a union-label article.

He reached the Somerset by a roundabout walk, passing more than one of his acquaintances with inward amusement at their failure to recognize him. He had arranged for Helene to invite Shine Taylor and Reginald Warren down to call on her at the apartment in the California at this particular time. So thus he felt that the coast was clear. At the tradesmen's entrance, where he had gone before to hoist on the dumbwaiter, he entered the building. An investigation of the basement showed him that in the rear of the building were one large and two small courts or air shafts. Then he ascended the iron stairway to the street level of the vestibule.

“Say, bo, I come to fix de pipes on de second floor,” was his self-introduction to the haughty negro attendant. “Dey're leakin' an' me boss tells me to git on de job in a hustle.”

“Which one? I ain't heard o' no leaks. It must be in de empty apartment in de rear, kase dat old maid in de front would been kickin' my fool head off ef she's had any trouble. She's always grouchy.”

“Sure, dingy, it's de empty one in de rear. Lemme in an' I'll fix it.”

“You-all better see de superintendent. People is apt to be lookin' at dat apartment to-day to rent it, an' he mightn't want no plumber mussin' round. I'll go hunt 'im fer you-all.”

“Say, you jest lemme in now. I'm paid by de hour. You knows what plumber bills is, an' your superintendent'll fire you if he has to pay ten dollars' overtime 'cause you hold me up.”

This was superior logic. The negro took him up and opened the door. Shirley entered, and peered out of the court window in the rear. Helene's suggestion about the dust was applicable here, for he found all the windows coated except the one opening upon the areaway. Below he observed a stone paving with a cracked surface. It was semidark, but his electric pocket-light enabled him to observe one piece of the rock which seemed entirely detached. Shirley investigated the closets of the empty apartment. In one of them he discovered the object of his search. It was a knotted rope. He first observed the exact way in which it had been folded in order to replace it without suspicion being aroused. Then he took it to the small window of the air shafts hanging it on a hook which was half concealed behind the ledge. Down this he lowered himself, hand over hand. The stone was quickly lifted—it was hinged on the under surface. In the dark hole which was before him there was an iron ladder. Down he went, into the utter blackness. His outstretched hands apprised him that he was at the beginning of a walled tunnel, through which he groped in a half-upright position. He reached an iron door, and remembering his direction calculated that this must be at the rear entrance of the old garage on West Fifty-fifth Street. It opened, as he swung a heavy iron bar, fitted with a curious mechanism resembling the front of a safe. Softly he entered, carrying his heavy boots in his hand. All was still within, and he shot the glow ray of his little lamp about him. As the reader may guess, it was the rear room of Warren's private spider-web! The table, facing the screen was surmounted by an ingenious telephone switchboard.

Shirley examined this closely. The various plugs were labelled: “Rector,” “Flatbush,” “Jersey City,” “Main,” “Morningside,” and other names which Shirley recognized as “central” stations of the telephone company. Here was the partial solution of the mysterious calls. He determined to test the service!

He took up the telephone receiver and sent the plug into the orifice under the label, “Co.” wondering what that might be. Soon there was an answer.

“Yes, Chief. What is it?”

“How's everything?” was Shirley's hoarse remark. “I find connections bad in the Bronx? What's the matter?”

“I'll send one of the outside men up there to see, Chief. There's a new exchange manager there, and he may be having the wires inspected. But my tap is on the cable behind the building. I don't see how he could get wise.”

Shirley smiled at this inadvertent betrayal of the system: wire tapping with science. He was able to trap the confederate with his own mesh of copper now.

“I want to see you right away. Some cash for you. I'm sick with a cold in the throat so don't keep me waiting. Go up town and stand in the doorway at 192 West Forty-first Street. Don't let anybody see you while you wait there, so keep back out of sight. How soon can you be there?”

“Oh, in half an hour if I hurry. Any trouble? You certainly have a bum voice, Chief. But how will I know it's you?”

“I'll just say, 'Telephone,' and then you come right along with me, to a place I have in mind. Don't be late, now! Good-bye.”

Shirley drew out the connection and tried the exchange labelled “Rector.” Instantly a pleasant girl's voice inquired the number desired.

“Bryant 4802-R.”

This was the Hotel California.

The operator on the switchboard of the hostelry replied.

“Give me Miss Marigold's apartment, please.”

Helene's voice was soon on the wire. Shirley asked for Warren in a gruff tone.

“What do you want?” was that gentleman's musical inquiry, in the tones which were already so familiar to the criminologist.

“Chief, dis is de Rat. I wants to meet you down at de Blue Goose on Water Street in half an hour. Kin you'se come? It's important.”

The other was evidently mystified.

“The Rat? What do you mean? I don't know you. Ring off!”

Shirley heard the other receiver click. He held the wire, reasoning out the method of the intriguer. Soon there was a buzz in his ear, and Warren's voice came to him. It was droll, this reversal of the original method, which had been so puzzling.

“What number is this?”

“Rector 4471, sir,” answered the criminologist in the best falsetto tone he could muster. Then he disconnected with a smile. This was turning the tables with a vengeance. But he knew that he must be getting away from the den before the possible investigation by Warren or his lieutenant. There were many things he would have liked to study about the place. But his curiosity about the telephone had made it impossible for him to remain. It was a costly mistake, as events were destined to prove!

He hurried out of the compartment, into the tunnel, up the rope and through the window. He replaced the knotted rope, exactly as it had been before. He put a few drippings of molten lead from the bubbling pot, under the wash-stand of the bathroom, to carry out the illusion of his work as plumber. Then he departed from the building, as he had entered.

In ten minutes he was changing his garments in Mike's plumbing shop, with a fabulous story of the excruciating joke he had played upon a sick friend. Then he walked rapidly to the doorway at 192 West Forty-first Street.

Back against the wall of this empty store entry, lounged a pleasant-looking young man who puffed at a perfecto. Shirley stepped in, and in a low tone, said: “Telephone.” The other started visibly, and scrutinized the well-groomed club man from head to foot.

“Well, Chief, you're a surprise. I never thought you looked like that. Where will we go?”

“Over to the gambling house a friend of mine runs, just around the corner. There we can talk in quiet.”

Shirley led the way, restraining the smile which itched to betray his enjoyment of the situation. The other studied him with sidelong glances of unabated astonishment. They were soon going up the steps of the Holland Agency, which looked for all the world, with its closed shutters, and quiet front, like a retreat for the worshipers of Dame Fortune. Cronin fortunately did not believe in signs. So the young man was not suspicious, even when Shirley gave three knocks upon the door, to be admitted by the sharp-nosed guardian of the portal.

“Tell Cleary to come downstairs, Nick,” said the criminologist. “I want him to meet a friend of mine.”

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.