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.