The Ark's chief astronomer altered its course so he could study a comet: now the debris is seriously damaging the Ark. The thrusters that can move it to safety need to be fixed manually, and Devon volunteers for EVA to do the work.

Garth leaves his friends and heads back home, only to find himself recruited into the Ark's police, who are working with the police of an alien system to avert an interplanetary war. But their efforts are being thwarted from within.