"Oh, I don't know." Old Tom was puffing as he kept up with the younger man's long strides. "We clear a bit of oricalchum from Mars, tungsten and commercial diamonds from Earth, plus a fair trade in jewels and other lightweight luxury items. Tourist traffic is brisk. We manage here, but we'll never get much farther without a better fuel.... Well, here comes the mail packet." A man in a lead-armored suit had run past them and was wigwagging with a checkered flag. Other men were sweating a twenty-ton cradle into the middle of the floor. Then the mechanics scuttled for the barriers. Frank and Tom followed their example. As they watched over the top of a thick wall surrounding the "field", a shutter in the center of the roof snapped open. They had a glimpse of the ship cushioning down on her atomic jets before they ducked out of range of the deadly gamma rays. "One nice thing about landing where there's no atmosphere," said Frank. "You don't have to shift to those confounded peroxide jets." He found that he was shouting, but that his voice sounded far-away and thin. Even with the comparatively small air loss through the shutter opening, pressure within the dome was dropping so rapidly that they found it difficult to breathe. The almost instantaneous loss of air and heat into the absolute zero vacuum of space caused a snowstorm to swirl within the dome. Then the rocket blaze died, the packet dropped neatly into her cradle and the shutter closed. "Whew! You really take a landing seriously," whistled the S.P. man. "What if a ship should miss the shutter and come down through another part of the roof?" "Don't mention it." Tom's voice was strained. * * * * * Frank stepped from behind the barrier to stare at the new arrival. She was a globe, probably twenty times the size of his one-man ship. She was painted a dead black on one hemisphere and a blazing white on the other so her interior temperature could be regulated by rotating the reflecting and absorbent surfaces toward the sun while in flight. She evidently had had a brush with a meteor, since one section of her hull was badly scratched and dented. The packet's port spun open. An eight-foot Martian in captain's uniform came tumbling out of it. "K. M! K. M! K. M!" the Martian was chanting in a magnificent baritone. His great chest pumping like a bellows and his downy red face covered with perspiration, he sprinted for the Communications Room. "Flash for all stations," he was singing as Frank and Tom hurried up to eavesdrop. "Captain Avron of Packet _Spaceblazer_ reporting. When I came out from under Suspenso two hours ago an unknown comb-shaped vessel was pacing the _Spaceblazer_." "Another ship in your orbit? And pacing a packet?" The K. M. man shook his head. "That's impossible, Captain."