"Four--shut the door," Barney's voice croaked weirdly. For complicated two-man disassemblies underwater, the traditional hand signals were not enough. The minisub acted as a telephone exchange. * * * * * Turning from the minisub, Barney plugged into the telephone connection in the wall of the chamber, giving them the word. From the way the Arctic Ocean, fire-hosed into the chamber, the Murderer guessed they had at least a hundred feet of water standing on them. This captain had no intention of smashing his periscopes on pack ice. Wryly, the Murderer grinned while the water crept up his body. He knew the limiting factor in their search for a picket buoy, any picket buoy, was the survival time in their air tanks. As for the minisub, it had the capability of keeping their corpses warm for several hours thereafter. With its gyroscope efficiently clicking commands to the rudder, it would maintain a straighter course than any man could steer. If it could eat fish and reproduce itself.... The waterline rose above his glass face-plate. On the curved ceilings of the chamber, the air shrank into a squirming bubble. The pressure had been equalized. There was a cold metallic screech as Barney opened the outer hatch into the Arctic Ocean. Valving an additional hiss of compressed air into the minisub's forward flotation tank, the Murderer gave it a gentle push and rode it out, his hand on the air release valve now to prevent the increasingly buoyant minisub from falling upward against the white-glaring underside of the ice pack. "There's a hell of a current up here," Barney's voice croaked. The Murderer glanced down, and his free arm clutched the cockpit in an anthropoidal fear-reflex of falling. The water was that clear. Down there, the submarine seemed to drift away like a great dirigible in the wind, but the Murderer knew the minisub was actually doing the drifting. "Tinker carefully with your gyroscope, Mr. Navigator," Barney laughed, "and we'll go take a look for your sea serpent." He gave Barney a straight course into the current. The Murderer had had nightmares of being lost under the arctic ice pack. "Keep an eye peeled on the ice," Barney muttered, but the Murderer kept both eyes on the instruments and gave Barney a one-hundred-eighty-degree change of course, trying to determine the speed of the current. "One way's as good as another," Barney laughed. Unfortunately, this had to be a visual search. The drawing-board boys had designed the picket buoys so they would _not_ be detected, and thoughtfully made them self-destroying in case they were. If anywhere near, a submarine would be recorded, and the under-ice warning system had actually worked against their own submarines. But the picket buoys in this sector, one by one, had died without a warning sound except, as scuttlebutt would have it, a toothy crunch. "This pack ice has changed," Barney's voice muttered.