Synopsis: From the Flyleaf: Pegasus, America's first spacecraft large enough to be called a ship, is scheduled to depart soon for Mars. The spaceship's commander is Colonel Ike Sanborn (introduced in Marooned in Orbit). Her mission is the most difficult yet attempted by man in space, and for this reason her entire crew has gone through the most careful kind of screening--both physical and psychological. In spite of these painstaking precautions one man has slipped through the net, an individual who may cause serious trouble on this, man's first journey to the Red Planet.