An experimental rocket, the BR7, is sent thousands of miles over the Earth on a mission of observation. It has a fault in its controls, and its crew loses contact with the scientist who designed it, Professor Bernard Quatermass, who leads the mission control operations on the ground. After contact is restored, the rocket crash-lands in Wimbledon, and Quatermass and his British Experimental Rocket Group quickly go there to recover the crew, then must wait for the space vehicle to cool.

When the capsule opens, only one of the three crewmembers, Victor Carroon, emerges, then collapses. When he recovers, it is clear he cannot remember what happened to the others. It is also clear, however, that something of the missing crew lives on in another form...