When relief pilot John Barton is sent on an emergency rescue mission to an unexplored planet, he is shocked to find young Marilyn Cross hiding aboard his ship. Barton discovers they have only enough fuel to carry himself and his precious cargo, and Marilyn's added weight insures that they will crash if she stays on board. They have gone too far to turn back, and the computer calculations have made it brutally clear: Someone must go, or all will die.