The Ark craft "Pisces" has been on a mission to locate habitable planets for ten years, while on the Ark, 409 years have passed. The Ark's chief astronomer had changed the Ark's course so he could study a comet: Unfortunately, debris has damaging the Ark.
| Actor | Role |
|---|---|
 Keir DulleaDevon | Devon |
 Gay RowanRachel | Rachel |
 Lloyd BochnerCol. M.P. Garoway | Col. M.P. Garoway |
| CCarol LazareNavigator Teale | Navigator Teale |
 Diana BarringtonJanice | Janice |
| WWilliam OslerComputer | Computer |
| LLillian GrahamOld Woman | Old Woman |
| SSusan FlemingTech | Tech |
 Edward AndrewsLinus Farthing | Linus Farthing |
 Linda SorensenDoctor McBride | Doctor McBride |
 Allen Stewart-CoatesComputer voices | Computer voices |