It was Kreiss standing down there who first caught Chet's attention. Kreiss was trying to shout. Chet saw his waving arms; he stared, puzzled, at the facial contortions--the working lips from which no sound came. He knew that something was wrong. It was a moment or two before he realized that Kreiss could not speak, that the throat, injured by the choking fumes, had failed him. Then he heard the strangled croak that Kreiss forced from his lips: "_Behind you!--look behind you!_" Schwartzmann was scrambling to the top where they stood; every man was accounted for. What had they to fear? And suddenly it was borne in upon Chet's consciousness that he had been hearing a sound--a sound that was louder now--a rustling!--a clashing of dry, rasping things! The very air seemed to hold something ominous. He knew this in the instant while he whirled about; while he heard the dry rustling change to a humming roar; while he saw, like a cloud of flame, a great swarm of red, flying things like the one that had flown past the port--and one, swifter than the rest, that darted from the swarm and flashed upon him. [Illustration: _One, swifter than the rest, dashed upon him._] It was red--vividly, dazzlingly red! The body of a reptile--a wild phantasm of distorted dreams--was supported by short, quivering wings. The body was some five feet in length, and it was translucent. A shell, like the dried husk of some creature long dead!--yet here was something alive, as its quick attack proved. It had a head of dry scales which ended in a projecting black-tipped beak that came like a sword, straight and true for Chet's heart. It seemed an age before he could bring his pistol up and fire. * * * * * Detonite, as everyone knows, does not explode on impact; the cap of fulminate in the end of each bullet sets it off. But even this requires some resistance--something more than a dry, red husk to check the bullet's flight. There was no explosion from the tiny shell that Chet's pistol fired, but the bullet did its work. The creature fell plunging to the rocky ground, and its transparent wings sent flurries of dust where they beat upon the ground. There were others that went down, for the bullet had gone on and through the great swarm. And then they attacked. The very fury of the assault saved the huddle of humans. So close were the red things pressed together that their vibrating wings beat and locked the swarm into a mass. They were almost above their prey. Chet knew that he was firing upward into the swarm, but the sound of his pistol was lost. The red cloud hung poised in a whirling maelstrom; and the pandemonium of clashing wings whipped down to them not only the sound of their dry scraping but a stench from those reptile bodies that was overpowering. Sickly sweet, the taste of it was in Chet's mouth; the sound of the furious swarm was battering at his ears as he knew that his pistol was empty.