Influenced by the social and geopolitical situation of the early 1970s and the hippie youth movement of the late 1960s, "Quatermass" is set in a near future in which large numbers of young people are joining a cult, the Planet People, and gathering at prehistoric sites, believing they will be transported to a better life on another planet. The series begins with Professor Quatermass arriving in London to look for his granddaughter, Hettie Carlson, and witnessing the destruction of two spacecraft and the disappearance of a group of Planet People at a stone circle by an unknown force. He investigates this force, believing that Hettie may be in danger. As the series progresses, it becomes apparent that the Planet People are being harvested rather than transported.