"The planes and the rest of the hangar look all right," he said. "It"s just us and the sedan that"s green. Why is that?"
"It"s because you walked through the grayish fog, that came from those cylinders you threw out of the window," Doc explained. "The car was driven through the fog, too."
"Velvet and Biff also drove through it," Monk e.j.a.c.u.l.a.t.ed.
"Which should make it simple for us to find them," Doc said dryly. "Touring cars are scarce this cold day.
The chances that more than one drove past that skysc.r.a.per while the fog was in the street, are very slim indeed. Look for a touring car which shows green under the ultra-violet light."
It was not necessary for Doc Savage to go into a detailed recitation concerning ultra-violet light. His men had seen it in operation before. Doc used it a great deal.
Ultra-violet light, being outside the visible spectrum, does not register on the retina of the eye; for that reason it is sometimes called "black light."
Certain substances, however, behave strangely when exposed to ultra-violet light. They fluoresce, or glow, in unearthly hues. Ordinary vaseline and aspirin are two substances which behave thus.
The chemicals which composed Doc"s strange fog were another. He had developed the stuff by careful experimenting. Its propensity for this glowing phenomena was extremely p.r.o.nounced.
The tiny quant.i.ties of the grayish vapor, deposited on bodies moving through it-such as walking men and moving automobiles-was sufficient to glow in a very brilliant fashion.
Doc Savage pressed a b.u.t.ton. This set an electric motor in operation, and opened the vast rear doors. The hangar floor sloped down into the river. There was a small film of ice on the water. The first plane to enter-the great tri-motored high-speed amphibian, with Renny at the controls-broke the ice.
In rapid succession the planes took the air. There was a craft for each man.
Every ship was fitted with a powerful ultra-violet light projector. These had been installed for a long time. This was not the first time Doc had used ultra-violet light. It was, however, his initial experiment in tracing men who had merely walked through a fog of Doc"s own making. The six planes scattered to the northward-Velvet and Biff had driven north.
The projectors of ultra-violet light were turned on. These were of Doc"s own design, and extremely powerful.
The ships flew low. At times they literally banked around skysc.r.a.pers, spires.
Monk, spotting a car which glowed green below, all but collided with a high building. He flew down into the canyon of a street, frightening stenographers and the inevitable clouds of pigeons which swarmed around the rooftops.
"Blast it!" Monk grumbled, and zoomed upward again.
The car he had discovered was a convertible. No doubt it had chanced to drive through the vapors surrounding Doc"s skysc.r.a.per headquarters.
The hunt worked steadily northward.
EACH of Doc"s five men was flying a different plane. Doc himself, however, had taken up the strangest crate of the lot. At first glance this seemed merely an auto-gyro.
An airman would have immediately noticed something unusual about the craft, however. For one thing, the taila.s.sembly had no control surfaces. There was merely a fishtail effect. The two stubby wings usually supplied on auto-gyros were missing.
Doc"s craft was a true-gyro. In the hands of a pilot sufficiently skilled, it could land on a table top, and take off from the same point.
Doc Savage sent his unusual ship ahead of the others. He selected one of the main arterial streets, and traced it. If Velvet and Biff had parked their car downtown, one of Doc"s men would probably locate it. Doc himself hoped to overhaul the pair if they had kept driving.
Doc saw no sign of a touring which showed a weird color under the powerful ultra-violet light. He widened the sphere of his search. Touring cars were very scarce.
For fully an hour they hunted.
The planes were fitted with radio-telephone transmitters and receivers. These sets were supplied with Doc"s version of what is popularly known as "voice-scramblers." These contrivances distorted voice sounds at the transmitting end, and straightened them out at the receiver.
Any one tuning in on Doc"s interplane conversation would not have been able to understand a word of it.
By radio, Doc ascertained his men had found nothing.
"Biff and Velvet have done one of two things," Doc decided. "Either they drove their car into a garage, or they hurried straight out of town."
"They sure don"t seem to be on the streets below," Monk agreed. He spoke as if they were in the same room, instead of being widely separated in the frosty sky.
"Let"s look the airports over," Doc suggested.
"Maybe they lit out along some country highway," Renny"s thunderous voice offered.
"In that case, they will be easy to catch," Doc told him. "The storm last night blocked the roads with snow.
They have not yet been cleared."
The six planes whipped away in various directions, each seeking an airport.
It was Doc who sighted the curtained touring car. He discovered it near a big airport in New Jersey. It was headed toward town, not away from it.
Doc swung his gyro along above the car, matching the car"s speed. At the same time he descended swiftly.
The gyro motor was efficiently m.u.f.fled. It was unlikely that those in the car would hear it.
Something over which Doc had no control betrayed his presence. The men in the coach saw the shadow which his plane cast on the snow.
The rapid approach of the shadow alarmed them. They thrust heads out, looked upward, and saw Doc.
Gun muzzles sprouted from the car curtains. They lipped flame.
DOC jerked his head inside the gyro. Bullets snapped at the spinning wing-vanes. Slugs drummed fiercely against the underside of the fuselage. They hammered staccato thunder. The concussions were so regular that Doc knew one of the weapons below was a machine gun.
The gyro cabin was fitted with a thin, very tough alloy armor. A high-powered rifle bullet, hitting squarely, would have penetrated it. The armor was effective against the weapons below, however.
Doc shifted the lever which controlled his forward speed. He shot ahead of the touring car. Then he touched another lever. This caused a mechanism to click.Hollow tubes projected from the gyro hull. These spat slender aero bombs. Striking the snow-covered pavement ahead of the touring car, the bombs turned into great mushrooms of bilious-colored smoke.
The car plunged into the vapor. The driver had locked the brakes, and the car slewed from side to side.
The automobile skidded off the pavement, plowing up snow. It came to a stop, half buried in the flake-filled ditch.
Doc dropped his gyro near the machine. The snow was over his knees. He plunged through it, got a look inside the touring car, and his haste evaporated.
The girl, Tip Galligan, was not in the machine. Nor were Velvet and Biff present.
It was a villainous-looking crew which the touring car bore. They numbered seven. Small-time crook was stamped on the face of every man.
They were all unconscious from the effects of the gas, loosened by Doc"s aerial bomb.
Returning to the gyro Doc switched on the radio transmitter. "I bagged the car," he reported. "The big game wasn"t in it, though. Come on over."
He gave his location before he switched off the transmitter. Then he returned to the ditched car.
Looking the unconscious men over, Doc selected the one with the weakest mouth. He produced a hypodermic needle from a black case, and used it on the man he had selected.
Almost at once, the fellow began to stir with returning wakefulness. The stuff which Doc had injected was a stimulant, and also neutralized the effects of the gas itself.
The man opened his eyes, took one look at Doc, and closed them again, as if he had seen a spike-tailed devil.
"I didn"t do it!" he moaned weakly.
"Do what?" Doc demanded.
What followed was weird-the man talked freely, if thickly, and in a tone hardly understandable. This was due to the stupefying effects of Doc"s gas. At first it was doubtful if the man quite realized what he was saying.
Afterward, when he did comprehend, he saw he was in too deeply, and kept on talking.
"Didn"t murder John Acre," whined the man.
"You were in the hangar raid?" Doc demanded.
"Uh-huh," mumbled the fellow.
"Where is the girl, Tip Galligan? Where are Velvet and Biff?"
"They lit out," said the man thickly. "Boss gave "em orders."
"Who is the boss?"
The man rolled his eyes. It was just dawning on him that he was talking too freely. "Mister, I"m tellin" you these things because I"m an innocent guy who just happened to get in with the wrong crowd. Them fellers didn"t tell me anything. I don"t know who the big shot is."
"Was he here in New York?"
"Maybe. I ain"t sure. Velvet and Biff got their orders from him by telephone. Maybe they used long distance. I ain"t sure."
"How many left in the plane?" Doc asked.His source of information batted eyes. "Gosh, how"d you know they went in a plane?"
"The fact that you fellows were on the airport road could hardly mean anything else," Doc replied. "How many took off in the plane?"
"The girl, Velvet, and Biff were all we saw. We had been holdin" the dame, and we took her to the airport.
Velvet and Biff carried her to the plane. There might have been somebody else in the ship. We couldn"t tell.
We didn"t go very close."
"What kind of a plane?"
"A yellow bus. It looked fast."
"Where were they heading for?"
"I dunno," said the man. "Me and me pals here are just some guys Velvet and Biff hired to kinda help out."
Doc"s bronze features remained expressionless. He was reasonably sure the man was telling the truth.
Velvet and Biff and their mysterious chief were too clever to trust a weak-kneed specimen like this with important secrets.
IT was noon. The great inlaid table in Doc"s outer office was littered with maps. Various pieces of scientific equipment were stacked on the floor.
Monk and Long Tom were making this stuff ready for transportation. Their movements were grim and swift.
Monk rarely went long without a wisecrack, but he had attempted no verbal snapper for more than an hour.
Doc Savage was a.s.sembling information and issuing orders. Just now he was in telephone communication with Ham.
"I"m at the airport," explained the lawyer whose addiction was natty clothing. "That little thug told the truth about the yellow plane when he said it was fast. It"s a new crate, and extremely speedy. A guy here at the field sold it to Velvet early this morning."
"Did the airport attendants see how many were aboard when it took off?" Doc asked.
"No. It was cold. They were all gathered around the office stove. They did not notice the yellow plane until they heard the motor start. It was across the field, and they could not tell how many were in the cabin. They didn"t look close, anyway."
"Which way did it go? Any one remember that?"
"South."
Ham now gave a more detailed description of the yellow plane. This included the wingspread, the type of motor, the nature of the streamlining, and other details. Then Ham hung up.
Johnny, the tall and bony geologist, came in from the library. Johnny apparently did not know what to do with his eye-gla.s.ses which had the magnifying left lens, now that his vision was normal. He had them c.o.c.ked upon his forehead.
"I"ve checked over the geologic data on the section of the South American coast where that quake sank the destroyer," he announced. "I am more than ever convinced that a quake is an impossibility in that vicinity."
"There"s no doubt that they had one," Doc said dryly.
"It could not have been a natural quake," Johnny declared.
The phone rang. It was the thunderous voice of Renny."I spread a general alarm for that yellow plane as you suggested," he told Doc. "It seems we were just a bit too late. The crate took on a full load of gas at a flying field near Philadelphia. You know what that means."
"It means they can just about make it to Panama, nonstop," Doc said.
"Yeah," Renny agreed. "And they seem to be headed in that direction."
Immediately following his conversation with Renny, Doc jiggled the phone hook. He asked for a long-distance operator.