Since both Costigan and Bradley had often watched their captors at work during the long voyage from the Solar System to Nevia, they were quite familiar with the machine tools of the amphibians. Their stolen lifeboat, being an emergency craft, of course carried full repair equipment; and to such good purpose did the two officers labor that even before their air-tanks were fully charged, all the damage had been repaired. The lifeboat lay motionless upon the mirror-smooth surface of the ocean. Captain Bradley had opened the upper port and the three stood in the opening, gazing in silence toward the incredibly distant horizon, while powerful pumps were forcing the last possible ounces of air into the practically unbreakable storage cylinders. Mile upon strangely flat mile stretched that waveless, unbroken expanse of water, merging finally into the violent redness of the Nevian sky. The sun was setting; a vast ball of purple flame dropping rapidly toward the horizon. Darkness came suddenly as that seething ball disappeared, and the air became bitterly cold, in sharp contrast to the pleasant warmth of a moment before. And as suddenly clouds appeared in blackly banked masses and a cold, driving rain began to beat down in torrents. "Br-r-r, it's cold! Let's go in--Oh! _Shut the door!_" Clio shrieked, and leaped wildly down into the compartment below, out of Costigan's way, for he and Bradley also had seen slithering toward them the frightful arm of the Thing. Almost before the girl had spoken Costigan had leaped to the levers, and not an instant too soon; for the tip of that horrible tentacle flashed into the rapidly narrowing crack just before the door clanged shut. As the powerful toggles forced the heavy screw threads into engagement and drove the massive disk home into its bottle-tight, insulated seat, that grisly tip fell severed to the floor of the compartment and lay there, twitching and writhing with a loathsome and unearthly vigor. Two feet long the piece was, and larger than a strong man's leg. It was armed with spiked and jointed metallic scales, and instead of sucking disks it was equipped with a series of _mouths_--mouths filled with sharp metallic teeth which gnashed and ground together furiously, even though sundered from the horrible organism which they were designed to feed.