Subway excavations unearth a deadly force from beyond space and time.

Workmen building an extension to the London subway discover skulls and skeletons of what appear to have been subhuman creatures. Investigation by Dr. Roney and Barbara Judd of the Natural History Research Institute uncovers a strange missile, thought at first to be an unknown Nazi weapon of World War II. As work continues on the missile, rocket expert Professor Quatermass studies the history of the area and learns that it has always been associated with demons, dating as far back as the Roman invasion. Opening the missile, the scientists discover the bodies of locust-like creatures, which Quatermass maintains are dead Martians. Furthermore, despite the passage of millions of years, Quatermass believes that their evil force is still present. His theory is verified when a monstrous horned creature materializes above the excavation pit. This creature's sinister power is such that the mind of any human being approaching it becomes controlled and redirected by the Devil. Knowing that the future of mankind is threatened, Dr. Roney drives a large crane into the creature, causing it to disintegrate. In so doing, however, Roney sacrifices his own life.