The moment he finished speaking, Doc beckoned Renny. The two of them entered the skyscraper.

The others, Monk, Ham, Long Tom, and Johnny, remained outside. They would have to explain the shooting to the police. Radio-squad cars laden with officers were booting up from all directions.

There would be no trouble explaining. Each of Doc's five men bore the honorary rank of captain on the New York police force.

ENTERING HIS eighty-sixth-floor office, Doc secured the sprayerlike contraption which he had abandoned at the start of the fight down in the street.

'What's that doofunny?" Renny inquired. He, too, had never seen the sprayer of a contrivance before.

"I'll show you." Doc indicated a sticky material on the corridor floor outside his office door. This resembled extremely pale molasses. The color blended with the floor tiles so as to be hardly noticeable. "See that?"

"Sure," Renny replied. "But I wouldn't have, if you hadn't pointed it out."

"I chanced to have the foresight to spread that stuff outside the door when I left Monk here with Victor Vail," Doc explained.

"What is it?"

"I'm showing you. Take off your shoes."

Bewildered, Renny kicked off his footgear. Doc did likewise.

Doc now pointed the nozzle of his sprayer down the corridor — away from the pale molasses material. A shrill fizzing sounded. A cloud of pale vapor came out of the nozzle.

"Smell anything?"

"Not a thing," Renny declared.

Doc aimed a puff of the strange vapor at the molasses stuff.

"Smell anything now?"

"Ph-e-w!" choked Renny. "Holy cow! A whole regiment of skunks couldn't make a worse

Doc hauled Renny into the elevator.

"The stuff in this sprayer and the sticky material on the floor form a terrible odor when they come together, even in the tiniest quantities," Doc explained as the cage raced them down. "So powerful are these chemicals that any one walking through the stuff in front of the door will leave a trail which can be detected for some hours. That's why we took off our shoes. We had walked through it."

"But I don't see — "

"We're going to trail Victor Vail," Doc explained. "But cross your fingers and hope he didn't take a taxi, Renny. If he did, we've got to think up another bright way of finding him."

But Victor Vail hadn't taken a taxi. He had walked to the nearest subway, and entered the side which admitted passengers to uptown trains, feeling his way along the building.walls.

"We're sunk!" Renny muttered.

"Far from it," Doc retorted. "We merely drive uptown and throw our vapor in each subway exit until we find the odor which will result from its contact with Victor Vail's tracks."

Renny laughed noisily. "Ain't we the original bloodhounds. though!"

They tried the exits of seven stations. At the eighth, Doc's remarkable vapor, a chemical compound of his own making, combined with the other chemical left by Victor Vail's shoe soles, and gave them the nauseating odor.

"It goes down this side street!" declared Renny.

There were few pedestrians on the street at this late hour. Even these, however, promptly stopped to gawk at Doc and Renny. It might have been the fact that Doc and Renny were without shoes, and going through the apparently idiotic process of spraying an awful perfume on the sidewalk.

More likely, it was Doc's mighty bronze form which caught their eye. Doc was a sensation whenever he appeared in public.

"What puzzles me is how the blind guy got around like this," Renny offered.

"Simply by asking help of those near him," Doc retorted. "Every one is glad to aid a blind man."

Renny got tired of the crowd of curious persons trailing them.

"Scat!" he told the rubberneckers violently. "Ain't you folks got a home you can go to?"

Renny had a most forbidding face. It was long. thinlipped, serious, and grim. Meekly, awed by that puritanical countenance, the crowd melted away.

Five minutes later, Doc and Renny halted before a door on which a plain gilt sign said:

DENTIST.

"He went in there, Doc," said Renny.

LIKE TWO dark cotton balls before a breeze, Doc and Renny drifted into the shadows. This district was a moderate residential section. The buildings were neat, but rather old, and not showy.

"Wait here," Doc directed. Doc was always leaving his men behind while he went alone into danger. Long ago, they had become resigned to this, much as it irked them to stand back when excitement offered. They literally lived for adventure.

But no one could cope with danger quite as Doc could. He had an uncanny way of avoiding, or escaping from, what for another man would be a death trap.

Around to the rear of the brick building, Doc glided. He found the back door. It was not locked inside — it was bolted. Heavy iron bars crisscrossed it.

Doc leaped upward. The height of that tremendous spring would have astounded an onlooker. He clutched an extended ledge and worked his way to a window on a second-floor hallway, with hardly more sound than the noise of a prowling cat.

The hall was dark. Doc drew things from his pockets. Some sticky gum, he affixed to the windowpane. Then a faint, gritty hiss sounded.

Doc had cut the glass cut of the window! He kept it from falling inward by the gum he had stuck to it. He eased inside.

Silence gripped the interior of the house. Doc prowled noiselessly. Only one room held a light. It was downstairs. The door was locked.

Doc let Renny in. They went to the fastened door.

"We might as well go in there all of a sudden!" Doc breathed.

"0. K., Doc," murmured Renny.

He lifted his gallon of iron-hard knuckles. He struck. With a rending crash, the door panel was driven inward by Renny's great fist.

They sprang into the room. Renny held a gun. Doc's powerful bronze hands were empty.

Horrified surprise halted them.

Only two men were in the room. One was Victor Vail. The other, as denoted by the sanitary smock he wore, was obviously the dentist who had his place of business here.

Both men hung suspended by ropes around their necks from a stout ceiling chandelier.

THE SUN was up. Doc's remarkable companions lounged in the skyscraper office. They had lost a night's sleep, but showed no effects of it.

Ham was honing the blade of his sword cane to a razor edge, looking ominously at Monk each time he tested its sharpness. Monk sat in an easy chair, reading a pocket manual of how to raise hogs. He took pains to hold the book so Ham could see the title. Monk often maintained — always within earshot of Ham — that some day he was going to retire and raise pork for a certain finely dressed lawyer he knew. Johnny, the archaeologist, was penning a chapter in the book he was writing on the ancient Mayan civilization.

Long Tom, looking pale as an invalid, was in the laboratory, humped over an apparatus which for intricacy would have given Steinmetz a headache.

Truly an amazing crew, these men.

Doc Savage entered. With him was Victor Vail. Renny walked in after them.

The blind man's neck was swollen somewhat where the rope had nearly strangled him to death — Doc had arrived just in time to save him.

The explanation of Vail's situation was quickly made.

"The dentist don't know a thing about the gang that seized him," Doc concluded. "They called him to the door and cracked him over the head."