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. 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. 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. The lightning strikes the stadium.