The propeller of the mysterious plane ahead had roared over. Its clamp had left the rack; it had dropped down in a perfectly controlled dive and flattened out as if a master pilot were at its controls.
But the plane's cockpit was still empty, Chris could see; nor had he seen any figure pass down the ladder from the dirigible into it!
Devoid of all emotion save bewilderment, he sat stupidly in the scout. A moment later, so well had he aimed it, its clamp nestled snugly into the groove of the rack, and the regular automatic action took place. A tiny door slid open directly above in the dirigible's hull: a thin ladder craned down—and Chris's nostrils caught a faint whiff of something that cleared his mind of its confusion instantly.
Just a whiff, but it registered. Gas, with an odor resembling carbon monoxide.
He stared up. Over the edge of the automatic trap-door above, a white, contorted face was hanging. The dirigible swung; white-clad shoulders and body slumped into view. Then, with a rush, the body slipped through, jarred against the connecting ladder, slithered off and went twisting and turning into the gulf below.
"God!"
Gassed! How, by what, Chris had no idea. A moment before he had been about to follow the uncannily piloted plane; but now his duty was plain. He knew with awful certainty that in minutes, seconds perhaps, the giant ZX-1 was scheduled to roar into flames like its sister and plunge into the Pacific.
He jerked out a gas mask. He was fitting it on with one hand as, with the other, he hauled himself up the spider ladder into the hull of the thundering, yawing dirigible.
He did not see, hovering a few hundred yards behind the ZX-1, the mystery plane; he did not see it now begin to approach the rack once more.