London, the near future. Dropped off at night in a desolate, deserted street by a taxi driver who refuses to go further, an old man finds himself surrounded by a gang of men, who threaten him with murder, until a car appears and they scatter. It emerges that the old man, who introduces himself as Professor Quatermass, and the driver, Dr. Joe Kapp, are both on their way to the nearby television studio.

The two arrive at the studio, where they are appearing in a live international broadcast to mark the connection of a new US/Soviet space station. The professor confides in Joe that his real interest is to find his missing teenage granddaughter.

For the interview, they are joined by satellite link-up by American ex-astronaut Chuck Marshall, a friend of the professor. When the interviewer asks Quatermass his feelings about the space station, he launches into an attack on US corruption and Russian tyranny, predicting the collaboration will end in disaster, before taking out a photograph of his granddaughter and appealing for help to find her. The link is cut before he can finish.

Moments later, the space station begins to experience problems, before breaking apart, to the astonishment of those watching. Over the satellite link, Marshall demands to know what inside information Quatermass had about the disaster. Quatermass protests his innocence.

Sneaking out, Joe drives Quatermass through a disintegrating London. Later, they encounter a group of 'Planet People' - young cultists who believe they can escape Earth to another world beyond the stars. Quatermass asks them if they have seen his granddaughter, but they are hostile and uninterested.

Arriving at Joe's country retreat the next day, Quatermass meets Joe's team of his scientists, his wife Clare and their two young daughters. Using their satellite equipment, the team have picked up strange extraterrestrial signals, coinciding with the destruction of the space station.

Joe and Clare take Quatermass to a nearby stone circle, Ringstone Round, where they find a crowd of Planet People and a unit of armed police trying to hold them back. Quatermass tries to reason with the mob, but the situation quickly deteriorates into a riot. As Quatermass and the Kapps make their escape, they hear a terrible noise, followed quickly by a blinding light focusing on Ringstone Round. Back at the stone circle, the crowds have people have vanished, with only ash remaining in their place.