
Set in the near future against the background of a British space programme, it tells the story of the first crewed flight into space, supervised by Professor Bernard Quatermass of the British Experimental Rocket Group.

A British experimental rocket orbits the Earth. After being out of contact for 57 hours, the capsule crashes back to Earth in Wimbledon, London. When the capsule is opened, only one member of the three-man crew emerges, Victor Carroon.

Victor Carroon is subjected to various tests which indicate that he has taken on the identities of the other two men. Quatermass and Paterson find a gelatinous substance spread around the capsule's interior.

Carron is taken back to the crash site and a recording of what happened during the orbit is played back to him, with disturbing results. A group of journalists try to kidnap him, but he, in turn, attacks one of them as he begins to change.

Carroon takes refuge inside a cinema (where a spoof film 'Planet of the Dragons', is on screen). He then goes to a chemist where he appears to in pain and his hand is seen to be badly mutated.