The film's storyline concerns Quatermass's investigation of reports of hundreds of meteorites landing only in the Winnerden Flats area of the UK. His inquiries lead him to a huge industrial complex, strikingly similar to his own plans for a Moon colony. This top-secret facility is in fact the centre of a conspiracy involving the alien infiltration of the highest echelons of the British Government. Quatermass and his allies must now do whatever is necessary to defeat the alien threat before it is too late.