of life, droppedaway, speeding ever due west; the hazy dots and blur of smoke whichdenoted the motionless Black Fleet vanished. But Chris was in contactwith the fleet's flagship once more, through the compactradio-telephone set of his scout. As he flew, his eyes fixed steadilyon the plane ahead, he was rapping into the microphone the story ofwhat had happened. He told of the invisibility of the strangemarauder, of how accurately he had judged the time of his raids; ofhow he, Chris, had managed to prevent the destruction of the ZX-1.
"He uses a tremendously expansive gas resembling carbon monoxide," hewent on. "It seeps into every cranny of the dirigible, killingeverything. The crews got no warning; they didn't know what washappening; couldn't see him! Well, I managed to wound him on the ZX-1.He beat it. I'm following him. If he lasts out, he'll go to where hecame from, and we'll find out who's in back of all this. Let you knowwhere his base is soon as I get there. Keep listening. Okay? Right;signing off."
Silence, then, between the scout and the flagship far behind....
* * * * *
On--on Time passed. The scout's gas was down below the half-way mark.They had covered two hundred miles now at a speed just bordering threehundred. The plane ahead looked uncanny with its apparently emptycockpit, but Chris could see all too well that death was pressing atits invisible pilot. The big machine was literally staggering in itscourse as the hands on its control stick grew weaker; was yawingwildly, even as the ZX-1 had yawed after her crew had been slain byvapors they could not see.
"He's got to last out!" Chris muttered. "Got to!"
At that moment land appeared, and the fleeing plane altered itsnortheast course to due east with an abrupt jerk.
First it was a mere hazy line on the horizon; then it rose to a thrustof land, jutted with cloud-misted hill-tops. Then, as the two roaringspecks that were airplanes came closer, heavy tropical foliage becamedistinct, and white slashes of surf breaking on the shore. This wasthe Azuero Peninsula, most western point of the Republic of Panama.
Aside from one small cluster of wretched huts, it was practicallyuninhabited. Guarded by dense growth, only one or two of the dustypaths which passed for roads wandered aimlessly through its tangledcreepers, trees and bush. To the southeast was the broad Gulf ofPanama, doorway to the Canal; on the other sides this thumb of landwas surrounded by the reaches of the Pacific.
The plane was obviously nearing its eyrie--dropping lower and lower,losing speed and altitude; and also threatening each moment to tumbledown out of control into the smothering welter of olive-green below,with a dead, unseen body in its cockpit.
But where was the landing field? They were now over the very heart ofthe Peninsula, and still Chris, searching through his telescopicsight, could see nothing but the monotonous roll of jungle. They mustcome to it soon, or be over to the Caribbean Sea and the MosquitoGulf.
Then suddenly he started forward, staring. Of course there was nolanding field in sight. The mystery plane needed none. It possessedthe power of the helicopter: it could rise straight up or sinkstraight down.
From each one of the two knob-like projections on its upper wing thathad puzzled him previously, a propeller had risen and unfolded intolong, flat blades. They whirled in circles of light in the sun; andthe airplane beneath them poised, all but motionless, its mainpropeller swinging idly, and then began slowly to drop downwards.
But Chris, swooping nearby, was still perplexed. Dropping down towhat? There was only the dense tropical growth beneath. He could seeno trace of men, no clearing, however small, no base--nothing but thejungle.
"How in the dickens--" he began; and then stopped. At that moment thejungle's secret was revealed.
* * * * *
As the helicopter-plane dropped to within a few hundred feet of it, astrip of the sea verdure split in two and reared up. It looked, atfirst, like magic. But from aloft Chris saw the trick and how thecamouflage was worked. What appeared to be a slice of the jungle roofwas, in reality, a metal framework cunningly plastered with layers ofgreen growth. An oblong, some fifty by a hundred feet, it parted inthe middle like a bridge that opens to let a steamer through,revealing the lair of the plane.
Soon more was revealed. Two tiny, green-painted huts stood in theminute clearing, and a few white-clad figures were by them, staring upat the plane sinking down and at the other plane which soared abovelike a buzzing mosquito.
One of the dwarfed figures in white waved an arm. The others aroundhim darted into the left-side hut. Then the helicopter-plane's wheelstouched the small space allotted for it in the clearing, and thewhirling propellers halted.
"So that's the secret!" Chris muttered. He pulled the microphone ofthe radio-telephone to his lips and angled with the dials forconnection with the fleet hundreds of miles behind, meanwhile notinghis exact position on Azuero Peninsula. But before he spoke, somesixth sense bade him glance below once more.
An icy shiver gripped his body.
A thin slit had appeared in the roof of the left-side hut. A spot ofbright blue light was winking evilly inside it. And, though he couldnot hear it, Chris knew with terrible certainty that a shrill,impatient whining was piercing from the machinery of a weapon insidethat hut--a weapon whose fangs had forked close to him once before--aweapon which the winking eye of blue presaged.
It struck. But at the same instant Chris leaped desperately from thecockpit of the scout.
* * * * *
He leaped almost into the teeth of the blue-tinged ray which knifed upwith uncanny accuracy from the slit in the roof of the hut. He wasconscious of a flash of unearthly light, of terrible heat which camewith it. Only the force of his jump saved him. He pulled the ripcordof the 'chute strapped to him and jerked to a pause; then he wasswinging beneath a mushroom of white, trembling as he stared at thefate he had missed by a hair's breadth.
A web of spectral blue light had enveloped the abandoned scout. Theplane appeared to shudder, hanging almost motionless in thewraith-like mist. Then, with a crackle, the wings and tail shiveredinto countless fragments; the stripped fuselage nosed over and plungedearthward, a roaring mass of flames. A fiery comet, it screamed pastthe man who swayed beneath his 'chute, coming within a few hundredfeet of him and searing him with its hot breath. Then it drove intothe dense flanks of the jungle growth.
Soon only a charred skeleton marked the last landing field of a scoutof the dirigible ZX-1.
"And now, I guess," Chris whispered, "they'll turn that ray on me...."
But he had only been a thousand feet up when he jumped. Already he wasclose to the top of the jungle. The clearing and its huts disappearedfrom view; he was out of range of the swift-striking ray. And, hereflected, though the scout was gone, he was still free--and could getto the Canal....
But tropical growth is difficult to land in.
A moment later his swinging body crashed through the branches of atree, and he pitched forward, unable to control the impetus. A suddenshock of pain stabbed through his head and everything spun dizzilybefore him. He knew he was falling, jerking down as the parachuteripped on the boughs. There was another impact which drove allremaining consciousness from him.
Darkness washed over Chris Travers, lying limp beneath the shreds of asilky white shroud....
* * * * *
Electric light. A strong glare of it somewhere. A dull throbbing inhis head. Then, a voice, with queer, hissing s's, speaking very closeto him.
"Ah, yess. Look you, Kashtanov. He will be conscious soon, I think."
"You're a damned fool, Istafiev, to let him wake up," said anothervoice, cool and of easy correctness. "He'll see the machines. Andthese Americans are tricky--one can never tell."
"Tricky? Bah! This fellow is a service man; there are things I canlearn from him. Come, now, wake yourself properly, you! That glass ofwater, throw it on his face."
Kashtanov--Istafiev. Names that could belong to only one country, tothat huge
power overseas which was hovering, so said rumors, on thebrink of war, waiting only for a favorable opportunity to strike--thecountry which the war game around the Canal had been designed toimpress. Chris Travers' mind cleared just then with completecomprehension of who had schemed to send both dirigibles down and whohad built this secret lair on Azuero Peninsula.
Inwardly, he groaned. It was all too plain. The destruction of theZX-2 and the thwarted destruction of her sister had only been thefirst step of some gigantic plan which was to provide the opportunityfor the mighty fighting machine overseas to strike. And he, who mighthave balked it, had made a rotten landing from the scout and deliveredhimself, helpless by his own clumsiness, into the hands of these men.The self-accusation was bitter.
With their secret of invisibility, their deadly blue rays, what havoccouldn't they wreak, working from their cunningly concealed base?
And now they