The Quatermass Xperiment (US title: The Creeping Unknown) is a 1955 British science fiction horror film. Made by Hammer Film Productions, it is based on the 1953 BBC Television serial The Quatermass Experiment written by Nigel Kneale. Produced by Anthony Hinds and directed by Val Guest, it stars Brian Donlevy as the eponymous Professor Bernard Quatermass. Jack Warner, Richard Wordsworth and Margia Dean appear in supporting roles.
The plot concerns three astronauts launched into space in a rocket designed by Quatermass. The spacecraft returns to Earth with only one occupant, Victor Carroon (Wordsworth). Something has infected Carroon during the flight and he begins mutating into an alien organism which, if it spores, will engulf and destroy humanity. When Carroon escapes from Quatermass’s custody, the professor and his associates, including Inspector Lomax (Warner) of Scotland Yard, have just a few hours to track the creature down and prevent a catastrophe.