A team of scientists search for the origin and purpose of a mysterious capsule found on a building site.
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.
Routine tests on a traffic accident victim lead to shocking discoveries when the man's blood is found to be unidentifiable and x-rays reveal a disc embedded in his brain. His fabulous tale of being an escaped prisoner from an alien spaceship takes a turn for the sinister when the hospital staff realise that they're under a state of siege...
