"Thanks," Preston said bitterly. He watched as the pirate ships approached, longing to trade places with the men in the Patrol ships above and below him. Suddenly a bright spear of flame lashed out across space and the hull of Gunderson's ship glowed cherry red. "I'm okay," Gunderson reported immediately. "Screens took the charge." Preston gripped his controls and threw the ship into a plunging dive that dropped it back behind the protection of both Patrol ships. He saw Gunderson and Mellors converge on one of the pirates. Two blue beams licked out, and the pirate ship exploded. But then the second pirate swooped down in an unexpected dive. "Look out!" Preston yelled helplessly--but it was too late. Beams ripped into the hull of Mellors' ship, and a dark fissure line opened down the side of the ship. Preston smashed his hand against the control panel. Better to die in an honest dogfight than to live this way! It was one against one, now--Gunderson against the pirate. Preston dropped back again to take advantage of the Patrol ship's protection. "I'm going to try a diversionary tactic," Gunderson said on untappable tight-beam. "Get ready to cut under and streak for Ganymede with all you got." "Check." Preston watched as the tactic got under way. Gunderson's ship traveled in a long, looping spiral that drew the pirate into the upper quadrant of space. His path free, Preston guided his ship under the other two and toward unobstructed freedom. As he looked back, he saw Gunderson steaming for the pirate on a sure collision orbit. He turned away. The score was two Patrolmen dead, two ships wrecked--but the mails would get through. Shaking his head, Preston leaned forward over his control board and headed on toward Ganymede. * * * * * The blue-white, frozen moon hung beneath him. Preston snapped on the radio. "Ganymede Colony? Come in, please. This is your Postal Ship." The words tasted sour in his mouth. There was silence for a second. "Come in, Ganymede," Preston repeated impatiently--and then the sound of a distress signal cut across his audio pickup. It was coming on wide beam from the satellite below--and they had cut out all receiving facilities in an attempt to step up their transmitter. Preston reached for the wide-beam stud, pressed it. "Okay, I pick up your signal, Ganymede. Come in, now!" "This is Ganymede," a tense voice said. "We've got trouble down here. Who are you?" "Mail ship," Preston said. "From Earth. What's going on?" There was the sound of voices whispering somewhere near the microphone. Finally: "Hello, Mail Ship?" "Yeah?" "You're going to have to turn back to Earth, fellow. You can't land here. It's rough on us, missing a mail trip, but--" Preston said impatiently, "Why can't I land? What the devil's going on down there?" "We've been invaded," the tired voice said. "The colony's been completely surrounded by iceworms." "Iceworms?"