The conversation was unimportant, except in that it showed what a little-known country Hidalgo was. Yet the Central American republic was of no inconsiderable size.
The last box was finally in the plane. An airport worker closed the plane door. Because of the murky dawn and moisture on the windows, it was impossible to see into the pilot’s compartment of the great tri-motor plane.
A mechanic climbed atop the tin pants over the big wheels, and standing there, cranked the inertia starter of first one motor, then the other. All three big radial engines thundered into life. More than a thousand throbbing horsepower.
The big plane trembled to the tune of the hammering exhaust stacks. It was not an especially new ship, being about five years old.
Perhaps one or two attendants about the tarmac heard the sound of another plane which had arrived overhead. Looking up, maybe they saw a huge gray bat of a shape go slicing through the mist. But that was all, and the noise of its great, muffled exhaust was hardly audible above the bawl of the stacks of the old-fashioned tri-motor.
The tri-motor was moving now. The tail was up, preliminary to taking off. Faster and faster it raced across the tarmac. It slowly took the air.
Without banking to either side, climbing gently, the big all-metal plane flew possibly a mile.
An astounding thing happened then.
The tri-motor ship seemed to turn instantaneously into a gigantic sheet of white-hot flame. This resolved into a monster ball of villainous smoke. Then flipped fragments of the plane and its contents rained downward upon the roofs of Jackson Heights, a conservative residential suburb of New York City.
So terrific was the explosion that windows were broken in the houses underneath, and shingles even torn off roofs.
No piece more than a few yards in area remained of the great plane. Indeed, the authorities could never have identified it, had not the airport men known it had just taken off from there.
No human life could have survived aboard the tri-motor aircraft.
DOC Savage merely blinked his golden eyes once after the blinding flash which marked the blast that annihilated the tri-motor ship.
“That was what I was afraid of!” he said dryly.
The rush of air thrown by the explosion caused his plane to reel. Doc stirred the controls expertly to right it.
For Doc and his men had not been in the ill-fated tri-motor plane. They were in the other craft which had flown over the airport a moment before the tri-motor took off. Indeed, Doc himself had maneuvered the take-off of the tri-motor, using remote radio control to direct it.
Doc’s radio remote control apparatus was exactly the same type used by the army and navy in extensive experiments, employing changing frequencies and sensitive relays for its operation.
Doc did not know how their mysterious enemy had managed to blow up the tri-motor. But thanks to his foresight, Doc’s men had escaped the devilish blast. Doc had used the tri-motor plane for a decoy. It was one of his old ships, almost ready to be discarded, anyway.
“They must have managed to slip high explosive into one of our boxes,” Doc concluded aloud. “It is too bad we lost the equipment in the destroyed plane. But we can get along without it.”
“What dizzies me,” Renny muttered, “is how they fixed their bomb to explode in the air, and not on the ground.”
Doc banked his plane, set a course directly for the city of Washington, using not only the gyroscopic compass with which the craft was fitted, but calculating wind drift expertly.
“How they made the bomb explode in the air can be simply explained,” he told Renny at last. “They probably put an altimeter or barometer in the bomb. The altimeter would register a change in height. All they had to do was fix an electrical contact to be closed at a given height, and—
bang!
”
“
Bang
, is right!” Monk put in, grinning.
Their plane flashed past the upraised arm of the Statue of Liberty, and sang its song of speed southward over the Jersey marshes.
Unlike the tri-motor which had been destroyed, this plane was of the latest design. It was a tri-motor craft also, but the great engines were in eggs built directly into the wings. It was what pilots call a low-wing job, with the wings attached well down on the fuselage, instead of at the top. The landing gear was retractible—folded up into the wings so as not to offer a trace of wind resistance.
It was the ultra in an airman’s steed, this supercraft. And two hundred miles an hour was only its cruising speed.
No small point was the fact that the cabin was soundproof, enabling Doc and his friends to converse in ordinary tones.
The really essential portion of their equipment was loaded into the rear of the speed-ship cabin. Packed compactly in light metal containers, an alloy metal that was lighter even than wood, each carton was fitted with straps for carrying.
In a surprisingly short time they picked up the clustered buildings of Philadelphia. Doc whipped the plane past a little east of the city hall—the center of the downtown business districts.
Onward they swept, to zoom down on an airport at the outskirts of Washington.
THE landing Doc made was feather-light, a sample of his wizardry with the controls. He tailed the plane about with sharp whirls of the nose motor, and taxied for the little airport administration office.
In vain did he look about for his autogyro. Ham should have left the windmill plane here, had he already arrived. But the whirligig ship was not in evidence.
An attendant, a spick-and-span dude in a white uniform, ran out to meet them.
“Didn’t Ham show up here?” Monk demanded of the man.
“Who?”
“Brigadier General Theodore Marley Brooks!” Monk explained.
The airport attendant registered shock, then great embarrassment at the words. He opened his mouth to speak, but instead, excitement made him merely stutter.
“What has happened?” Doc asked in a gentle but powerful tone that compelled an instant answer.
“The airport manager is holding a man over in the field office who says his name is Brigadier General Theodore Marley Brooks,” the attendant explained.
“Holding him—why?”
“The manager is also a deputy sheriff. We got a call that this fellow had stolen an autogyro from a man named Clark Savage. So we arrested him.”
Doc nodded absently. He was clever, this unknown enemy of theirs. He had decoyed Ham by a neat ruse.
“Where is the autogyro?” Doc asked.
“Why, this Clark Savage who telephoned the plane had been stolen asked us to send a man with it to bring him here and confront the thief!”
Monk let out a loud snort. “You dumb dude! You’re talkin’ to Clark Savage!”
The attendant stuttered again. “I don’t understand—”
“Some one foxed you,” Doc said without noticeable malice. “The pilot who flew that plane to get the fake Clark Savage may be in danger. Do you know where he went?”
“The manager knows.”
They hurried over to the administration building. They found a Ham who was burning up. Ham could ordinarily talk himself out of almost any situation, given a little time. But he hadn’t made an impression on the blond, bulletheaded airport manager.
Doc handed Ham a phone. “Get the nearest army flying field, Ham. See if you can raise me a pursuit ship fitted with machine guns. It’s against regulations, but—”
“Hang regulations!” Ham snapped, and seized the instrument.
From the blond airport manager Doc learned where the autogyro had gone to meet the man who had put over the trick. The spot was in New Jersey.
Doc located it on the map. It was in the mountainous, or, rather, hilly, western portion of Jersey.
Ham cracked the telephone receiver onto its hook. “They’re warming up a pursuit job for you, Doc.”
It required less than ten minutes for Doc to ferry over to the army drome, plug his powerful frame into a cockpit, saw the throttle back, and take off. He had a regulation war plane now.
FLYING northward, Doc had a fair idea of the purpose of their enemy in decoying the autogyro. The place was within motor distance of New York, so the villainous unknown one would probably be on hand. He would destroy the autogyro, thus hampering Doc and his friends all possible.
“Whoever it is, they’re willing to do anything to keep us from getting to that legacy of mine in Hidalgo!” Doc concluded.
Over the Delaware River, Doc dived and tested his machine guns by shooting at the shadow of his plane on the water.
Knobby green hills sprang up underneath. Doc used a pair of binoculars to scrutinize the terrain.
Farmhouses were scattering, ramshackle. Very few of the roads were paved.
Doc discovered his autogyro at last.
The windmill plane sat in a clearing. Near by ran a paved road.
In the clearing with the plane was a green coupe and two men. One of the men was holding a gun upon the other.
The gun wielder, Doc perceived when he came nearer, was masked. The man discovered Doc’s army pursuit plane, diving with motor cans a-thunder. The fellow took fright.
Deserting the other man, who must be the autogyro pilot, the masked fellow raced to the windmill plane. The gun in his fist spat a bullet into the fuel tank of the plane. Gasoline ran out in two pale strings. The masked man struck a match and tossed it into the fuel. Instantly the autogyro was bundled in hot flame.
One thing Doc noted about the masked man—the fellow’s fingers were a deep scarlet hue for an inch of their length!
The man was also squat and wide. He ran with shortlegged, pegging steps for the green coupe, dived into it. The green car ran out of the field like a frightened bug.
Doc’s cowl machine guns released a spray of lead that forked up dust behind the coupe. The car skewered onto the road and turned north.
Again Doc’s Browning guns tore off their ripping cackle of death. After the army fashion, every fifth bullet in the ammo cans was a phosphorous-filled tracer. These burst with hot red blots directly behind the green coupe.
Slowly, inexorably, the gray cobwebs of tracer smoke climbed into the rear of the automobile.
With a wild swing, the green car suddenly left the pavement. It vaulted a ditch, miraculously remaining upright, and skewered to a stop amid tall bush that practically hid it.
Doc distinctly saw the passenger quit the car and take to the concealment of the timber.
A couple of times Doc dived and let the Browning guns spew their twelve hundred shots a minute into the timber. He did it more to give the masked man one last scare than from any hope of bagging the fellow. The timber offered perfect concealment.
Not a little disgusted, Doc landed and launched a hunt afoot for the masked man. But it was too late.
The airport attendant who had flown the autogyro here could give no worthwhile description of the masked man when Doc consulted him. The fellow had merely sprung out of the green car with a gun.
Doc telephoned the authorities and had a net spread for the masked man before he took off again for Washington. But he was pretty certain the fellow would evade the Jersey officers. The man was smart, as well as very dangerous.
Doc took the chagrined airport attendant with him in the army pursuit plane back to Washington.
HAM and the others were waiting when Doc arrived, after restoring the pursuit plane to the army field.
“Have any trouble getting our papers up?” Doc asked.
Ham tightened his mobile, orator’s mouth. “I did have a little trouble, Doc. It was strange, too. The Hidalgo consul seemed very reluctant to O.K. our papers. At first he wasn’t going to do it. In fact, I had to have our own secretary of state make some things very clear to Mr. Consul before he gave us the official high sign.”
“What’s your guess, Ham?” Doc asked. “Was the official directly interested in keeping us out of Hidalgo, or had some one paid him money to make it tough for us?”
“He was paid!” Ham smiled tightly. “He gave himself away when I accused him of accepting money to refuse his O.K. on our papers. But I was not able to learn who had put the cash on the line.”
“Somebody!” Renny rumbled, his puritanical face very long. “Somebody is taking a lot of trouble to keep us out of Hidalgo! Now, I wonder why?”
“I have a hunch!” Ham declared. “Doc’s mysterious heritage must be of fabulous value. Men are not killed and diplomatic agents bribed without good reasons. That concession of several hundred square miles of mountainous territory in Hidalgo is the explanation, of course. Some one is trying to keep us away from it!”
“Does anybody know what they raise down in that neck of the woods?” Monk inquired.
Long Tom hazarded a couple of guesses, “Bananas, chicle for making chewing gum—”
“No plantations in the region Doc seems to own,” Johnny, the geologist, put in sharply. “I soaked up all I could find on the precise region. And you’d be surprised how little it was!”
“You mean there was not much information available about it?” Ham prompted.
“You said it! To be exact, the whole region is unexplored!”
“Unexplored!”
“Oh, the district is filled with mountains on most maps,” Johnny explained. “But on the really accurate charts the truth comes out. There’s a considerable stretch of country no white men have penetrated. And Doc’s strange heritage is located slap-dab in the middle of it!”
“So we gotta play Columbus!” Monk snorted.
“You’ll think Columbus’s trip across the briny was a pipe when you see this Hidalgo country!” Johnny informed him. “That region is unexplored for only one reason—white men can’t get into it!”
Doc had been standing by during the exchange of words. But now his calm, powerful voice commanded quick attention.
“Is there any reason we can’t be on our way?” he asked dryly.
They took off at once in the monster, low-wing speed plane. But before their departure, Doc telephoned long distance to Miami, Florida, where he got in touch with an airplane-supplies concern. He ordered pontoons for his plane, after determining the company kept them in stock.
THE approximately nine-hundred-mile flight to Miami they made in something more than five hours, thanks to the tremendous cruising speed of Doc’s superplane.