The story originally appeared in the November 1969 issue of the magazine Venture Science Fiction as "Plague Ship".

[3] On a routine trip to Mars, the passenger liner Johannes Kepler is hit by a meteoroid, killing the captain and almost all the senior members of the crew and resulting in the loss of much of the ship's breathable air.

Lieutenant Donald Chase, a junior medical officer, finds himself the highest-ranked surviving crew member and has to take over the running of the ship.

He is helped by Chief Petty Officer Kurikka, who is familiar with the technical aspects; the Mexican scientist Dr Ugalde, a passenger whose mathematical genius enables the new crew to navigate the ship; and various others.

Once the situation has stabilised, a passenger, General Mathew Briggs, who had criticised Chase's methods, overthrows him by force with the apparent help of Ugalde.