This is the book on which the 1969 movie by the same name was based. Gregory Peck starred as Charles Keith, the ground-based supervisor of a crew of astronauts led by mission commander Jim Pruett (Richard Crenna) conducting a series of endurance tests while in space. When Keith orders the ship to reenter earth's atmosphere, their craft experiences a mechanical problem, leaving the astronauts adrift. With the help of veteran astronaut and rescue specialist Ted Dougherty (David Janssen), Keith conceives a plan for saving the crew, whose lives are further endangered by the limited amount of available oxygen. Unfortunately, the takeoff of Dougherty's rescue craft is delayed by a hurricane. Realizing the crew's final hour might be at hand, Keith summons their wives in order to let them communicate with their spouses. During astronaut Buzz Lloyd's (Gene Hackman) conversation with his wife, he becomes hysterical, using up much of their oxygen in the process. Given the paucity of oxygen, Keith suggests that one of the crew might increase the chances for survival of the other two by offering to cut off his own oxygen supply. Understandably, this idea is not greeted with great enthusiasm.