Workers on the underground discover what looks like an old German World War II missile. When scientists establish that rather than German it is Martian and can draw out the evil in all humans, the world is thrown into chaos.
Workmen extending the London underground are shocked to what looks like a missile. When Professor Quatermass (Keir) and missile expert Colonel Breen (Glover) arrive they discover than instead of a remnant of the Second World War, it is in fact a five million-year-old Martian spaceship and Quartermass begins to unearth an eerie history of insect aliens who have influenced human evolution. Hammer Films adapted the third and best of Nigel Kneale's Quatermass serials a good decade after the first two, with a colourful studio feel instead of the black-and-white location eeriness of The Quatermass Xperiment and Quatermass II, but also with better acting and a less hysterical script.
It's a rare intelligent science fiction movie with genuine ideas to go along with its creepy moments.