The first manned expedition to Mars is invaded by an unknown life form, which stows away on the rescue ship.
| Actor | Role |
|---|---|
 Marshall ThompsonCarruthers | Carruthers |
 Shirley PattersonAnn Anderson | Ann Anderson |
 Kim SpaldingVan Heusen | Van Heusen |
 Ann DoranMary Royce | Mary Royce |
 Dabbs GreerEric Royce | Eric Royce |
 Paul LangtonCalder | Calder |
 Robert BicePurdue | Purdue |
 Richard BenedictBob Finelli | Bob Finelli |
 Richard HerveyGino | Gino |
 Thom CarneyKienholz | Kienholz |
 Ray CorriganIt | It |