The serial sees Professor Bernard Quatermass of the British Experimental Rocket Group being asked to examine strange meteorite showers. His investigations lead to his uncovering a conspiracy involving alien infiltration at the highest levels of the British Government. As even some of Quatermass's closest colleagues fall victim to the alien influence, he is forced to use his own unsafe rocket prototype, which recently caused a nuclear disaster at an Australian testing range, to prevent the aliens from taking over mankind.

• John Robinson
• Hugh Griffith
• John Stone
• Monica Grey
• Austin Trevor
• Ian Wilson
• Rupert Davies
• Edwin Brown