Episode list

Professor Quatermass comes out of retirement to search for his missing granddaughter and finds a world on the verge of anarchy, and an American-Russian space station destroyed by unknown forces. He is befriended by astronomer Joe Kapp and they witness the obliteration of thousands of Planet People by a beam of light at the stone circle, Ringstone Round.

Following the devastation at Ringstone Round, Quatermass hears of similar incidents worldwide and returns to London with district commissioner Annie Morgan and a Ringstone 'survivor' Isabel. En route they become separated in a shootout between rival gangs. Meanwhile, the beam of light descends again - near Joe Kapp's home.

Quatermass is rescued by a group of elderly people living in a scrap yard. At the hospital, the doctors are shocked when Isabel levitates off her bed and explodes in a cloud of dust. Elsewhere, the devastated Kapp is left alone in the ruins of his cottage and observatory. More and more young people are joining the Planet People, including the gangs that have been terrorising the cities and the soldiers assigned to keep them away from the Megalithic sites. Contact is restored with Chuck Marshall and with the Russians in the form of Gurov. Quatermass theorises that this is not the first time this has happened; megalithic sites such as prehistoric stone circles are in fact markers where beacons have been left by the alien force for its next visit. Quatermass believes the force is a sphere of energy surrounding the Earth. The Russians and the Americans send a space shuttle, commanded by Marshall, to make contact with the force. Quatermass is sceptical; he believes they are dealing not with an intelligence but with a machine constructed to harvest human protein. The space shuttle is destroyed but not before Marshall reports a giant beam of light stretching in all directions. Meanwhile, the Planet People are gathering at Wembley Stadium in the tens of thousands. Annie and Quatermass travel to the stadium but are powerless to prevent the Planet People from gathering. When they are attacked, Annie drives their car into the underground car park beneath the stadium where she crashes the vehicle and is killed. The lightning strikes the stadium.

Quatermass emerges from the car park to find the stadium empty. So many have now been harvested that the particles of dust in the air have turned the sky green. Kapp attempts to repair his equipment in order to contact the alien presence, but the Planet People destroy his efforts. They try to persuade him to join them but he refuses, convinced now that his family are dead. Quatermass, aided by Gurov, who has travelled to London from Moscow, assembles a team of scientists to find a solution. He deliberately selects old people for the task as they are immune to the effects of the alien force. Quatermass decides to set a trap. He plans to fake the presence of a large gathering of Planet People at Kapp's observatory and, when the force comes, to detonate a nuclear weapon. Quatermass does not believe this will be sufficient to destroy the alien machine but he hopes that it will damage it enough to make it go away. Kapp volunteers to stay behind with Quatermass to help detonate the bomb. The pair set up the trap and wait. Suddenly, Kickalong appears with a group of Planet People, including Quatermass' granddaughter, Hettie. Kapp tries to warn them away but is shot by Kickalong. The light appears, indicating that the alien force has arrived, but the shock of seeing his granddaughter among the Planet People causes Quatermass to suffer a heart attack. However, aided by Hettie, he is able to detonate the bomb. Later, according to Gurov, "The message was taken. It has not come again. We pray it will never come again."