Prof. Quatermass is resisting the planners of a grisly rocket project known as the Dead Man's Deterrent, But then comes an interruption - Excavation work at a building site in Hobbs Lane, London, unearths a human skull which Dr Roney estimates to be five million years old, Then a strange projectile is dug up.
Col. Breen believes the projectile is a bomb - it's cold to the touch, slightly radioactive and made of an unknown substance, Roney's assistant Barbara Judd finds the area has a history of supernatural events, and a terrified Pte West claims to have seen an imp-like ghost: 'It went through the wall!'.
Journalist James Fullalove helps Quatermass research the history of Hobbs Lane, finding its name derives from Hob - the devil. A technician, Sladden, succeeds in opening a sealed compartment in the capsule, revealing three petrified alien insects.
Roney and Quatermass develop their theory about the Martians' visit to Earth, instilling their essence into man's ancestors, Sladden, alone in the pit, flees in terror as strange forces are conjured up.
Chaos reigns in the pit and the long-dormant Martian inheritance begins to assert itself in many people in the area - including Quatermass himself - driving them to a new racial purge, The capsule breaks open and an energy form rises up over London. Roney finds he is immune and strives to defeat it.