Monk, Renny, Ham and Johnny were plunging through the door as Doc hung up. They had buckled on bulletproof vests. They had seized the small, deadly machine guns which were Doc’s invention.

Oliver Wording Bittman seemed dazed by the suddenness with which these men went into action. Swallowing his astonishment, he dived in their wake.

Doc summoned an elevator.

"Better take two taxicabs!" he advised when they were on the street. "If Kar should turn that Smoke of Eternity on one carload, it wouldn’t get us all."

"Pleasant thought!" Monk grinned.

The two cabs wheeled up Fifth Avenue. Doc rode the runningboard of the foremost machine. He habitually did this, for his very presence was a charm which magically gave him right of way through all traffic. New York City’s traffic policemen had been instructed by their chiefs to give every assistance to this remarkable man of bronze.

Too, Doc preferred to be outside where his keen eyes missed nothing. For this reason also, Doc’s personal cars were always roadsters or convertibles, the tops of which could be lowered.

The trip uptown turned out to be uneventful.

Long Tom, thin and sallow and looking like an invalid, but in reality as tough as any of Doc’s entourage, stood at a corner on Riverside Drive. His two boxes of apparatus were at his feet.

Doc had his cab pull up beside Long Tom.

"Where’d the wires go?" he asked.

Long Tom made a wry face. "I’m afraid we’re out of luck. The wires led from that tenth house, along the rear of other houses and went under Riverside Drive through a culvert. From there, they led underground down to that pirate ship, the Jolly Roger. They went aboard through a hawser, down to the keel, then into the water to — "

"To the tanklike submersible!" Doc said disgustedly. "So the wires in the room and on the boat were one circuit!"

"That’s it," Long Tom agreed.

DOC SAVAGE now shook his bronze head. "This is strange, Long Tom! When Kar talked to Monk, the fellow would hardly have been reckless enough to have done so from that room. He knew I had discovered the place."

"The secret phone circuit didn’t branch off anywhere," Long Tom said with certainty. He pointed at his instruments. "My thingamajig would have shown it if the wires were tapped anywhere."

Doc’s golden eyes ranged along the landward side of Riverside Drive. Apartment houses fronting the Drive were new and tall, although those on the side streets were not nearly so opulent. The Drive apartments commanded a view of the Hudson. They brought neat rentals.

Doc’s low, strange, trilling sound abruptly came from his lips. It was hardly audible now. Probably no one but Long Tom heard it. And Long Tom grinned. He knew this sound presaged some remarkable feat of Doc’s, for it came at the bronze man’s moments of greatest concentration. The sound with the weird, melodious quality of some weird jungle bird always precursed a master stroke.

"Let us do some investigating, brothers," Doc said softly.

He led them into the tenth house from the corner, which held in an upstairs room the end of the secret phone line. But Doc did not go upstairs. He guided the group out through a rear door.

Here was a long, narrow court. The place was untidy. Rickety old wooden fences marked off backyards hardly larger than good-sized bedspreads. Rusty clotheslines draped like old cobwebs.

The court resembled little else than a brick-walled pit. At the Riverside Drive end, the rear wall of a great apartment house towered many stories. At the opposite end was a lesser building. And on either side, the shabby sterns of old tenements buttressed each other solidly.

Evening was near. The hulking buildings threw shadows into the pit of a court.

Doc moved along the court, toward Riverside Drive. His sharp eyes soon located the secret phone wires. These followed the chinks between bricks for the most part. They had been coated with a paint the exact color of the brickwork.

They reached the wall of the immensely larger building which fronted Riverside Drive. Turning here, the thin, hardly visible strands traced along the rear of the structure.

At one point, a loop abruptly dangled out — a very small loop.

Doc pointed at this. "Notice anything peculiar about that?"

Long Tom stared.

"The insulation is gone at that point!" he ejaculated. "The naked copper of the wires shows!"

"Exactly. Note also that there are many windows directly above the spot."

"You mean Kar tapped them there and — "

"By reaching down and clipping the ends of other wires to them," Doc replied. "That means he did it from the window immediately above! Those loops are too small to be fished for from a greater distance."

To Renny and Johnny, Doc breathed a command. "You two stay here. Watch that window. Shoot at the slightest hostile move.

"The rest of you come with me!"

He led them swiftly around to the front of the apartment building which overlooked Riverside Drive.

THEY shoved past a bewildered doorman. The foyer was decorated elaborately. Deep carpet swathed the floor. It seemed quite a high-class establishment.

Doc described to the doorman the location of the apartment they suspected.

"Who lives there?" he asked.

"No one, yet," replied the doorman. "It was rented some time ago, but the tenant has not yet moved in."

Doc, Monk, Ham, Long Tom and Oliver Wording Bittman hurried up the stairs. Luxurious carpet made their footsteps noiseless. They reached the suspicious apartment.

Halting the others with an uplifted arm, some yards from the door, Doc advanced alone. He did not want them near enough that the sound of their breathing would interfere with his listening. For Doc’s ears were keen enough that he could detect the faintest respiration noises of men within the apartment.

He listened. Lowering close to the threshold, where there gaped a small crack, he used his nostrils. The olfactory senses of the average man are underdeveloped through insufficient use. He has no need for a super-keen organ of smell. Indeed, city life is more comfortable if the multitude of odors present go unnoticed. But Doc Savage, through unremitting, scientific exercise, had developed an olfactory sense far beyond the common.

Doc’s ears and nostrils told him no one occupied the apartment. He tried the door. Locked! He exerted what for his great muscles was moderate pressure. The door swished inward, lock torn out.

Not only was the place untenanted, but it held no furniture. The bare, varnished floor glistened faintly in the light of approaching evening.

Doc glided to the window. He waved at Renny and Johnny in the brick-sided pit of a courtyard below. His gesture advised them to stay where they were.

Back to the door, Doc whipped. His movements seemed effortless for all their speed.

Although there was no sign of a wire by which the secret phone line had been tapped, Doc was not satisfied. His trained brain told him where to look.

He tugged at the corridor carpet immediately outside the door. It came up readily.

The ends of two fine wires were revealed.

"They used a splice long enough to reach from these through the window!" Doc told the others.

Wrenching up the carpet, he followed the wires down the corridor.

Oliver Wording Bittman was white-faced. The flesh on his big jaw looked hard as rock. But he was not trembling.

"I am unarmed," he said jerkily. "C-can one of you loan me a gun? One of those c-compact machine guns! I want to do my part to wipe out those fiends!"

Doc reached a quick decision. It was his duty to take care of Bittman’s life, a repayment for the man’s service to his father.

"We neglected to bring along an extra gun," he said. "If you wish to help, you might hurry down and call the police."