The rush of wind had cleared his brain; his faculties were steady and normal. Not so with the man in the plane he pursued. It was flying crazily, but clinging to one course, nevertheless—into the northeast, towards land, some two hundred and fifty miles over the horizon.
The great silver shape of the ZX-1, barren, now, of life, dropped away, speeding ever due west; the hazy dots and blur of smoke which denoted the motionless Black Fleet vanished. But Chris was in contact with the fleet's flagship once more, through the compact radio-telephone set of his scout. As he flew, his eyes fixed steadily on the plane ahead, he was rapping into the microphone the story of what had happened. He told of the invisibility of the strange marauder, of how accurately he had judged the time of his raids; of how he, Chris, had managed to prevent the destruction of the ZX-1.
"He uses a tremendously expansive gas resembling carbon monoxide," he went on. "It seeps into every cranny of the dirigible, killing everything. The crews got no warning; they didn't know what was happening; 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 he came from, and we'll find out who's in back of all this. Let you know where 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 three hundred. The plane ahead looked uncanny with its apparently empty cockpit, but Chris could see all too well that death was pressing at its invisible pilot. The big machine was literally staggering in its course as the hands on its control stick grew weaker; was yawing wildly, even as the ZX-1 had yawed after her crew had been slain by vapors they could not see.
"He's got to last out!" Chris muttered. "Got to!"
At that moment land appeared, and the fleeing plane altered its northeast course to due east with an abrupt jerk.
First it was a mere hazy line on the horizon; then it rose to a thrust of land, jutted with cloud-misted hill-tops. Then, as the two roaring specks that were airplanes came closer, heavy tropical foliage became distinct, and white slashes of surf breaking on the shore. This was the Azuero Peninsula, most western point of the Republic of Panama.
Aside from one small cluster of wretched huts, it was practically uninhabited. Guarded by dense growth, only one or two of the dusty paths which passed for roads wandered aimlessly through its tangled creepers, trees and bush. To the southeast was the broad Gulf of Panama, doorway to the Canal; on the other sides this thumb of land was surrounded by the reaches of the Pacific.