The first manned expedition to Mars is invaded by an unknown life form, which stows away on the rescue ship.
Marshall Thompson
as Carruthers
Shirley Patterson
as Ann Anderson
Kim Spalding
as Van Heusen
Ann Doran
as Mary Royce
Dabbs Greer
as Eric Royce
Paul Langton
as Calder
Robert Bice
as Purdue
Richard Benedict
as Bob Finelli
Richard Hervey
as Gino
Thom Carney
as Kienholz
Ray Corrigan
as It
