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.