The spaceship Johannes Kepler is travelling the routine 92-day trip between Lunar Station and Mars when it is hit by a meteorite. The Captain and all senior crew members were holding a meeting and were killed by the impact. The only officers left are First Engineer Holtz, who refuses to leave the engine room and Lieutenant Donald Chase, a young doctor in his first post.

Chase finds himself in charge of a badly damaged ship, with a crew trained simply to obey orders, and over 100 passengers on the brink of panic. The novel follows his attempts to improvise solutions to problems which arise as they nurse the ship on towards Mars.

Dedication: To Barry L. Lewis, M.D., F.A.C.A.