"Force of Life" is the ninth episode of the first series of . The screenplay was written by Johnny Byrne; the director was David Tomblin. The original title was "Force of Evil". The shooting script is dated 15 May 1974; the final shooting script is dated 24 May 1974. Live-action filming began Wednesday 29 May 1974 through Friday 7 June 1974. After a three-week hiatus, filming resumed Monday 1 July 1974 through Friday 5 July 1974; the hiatus was planned, as the Landaus' contract guaranteed them time off for a summer holiday.
Story
The body of Anton Zoref is invaded by an unknown life-force. The man soon manifests an uncontrollable ability to absorb heat. As the Alphans struggle to understand this mysterious force, Zoref's need becomes insatiable. Driven by instinct, he freezes Mark Dominix, Hilary Preston and the security guard dead until he makes his way to the greatest source of heat on Alpha—the Nuclear Generating Plant. The force leaves Moonbase Alpha and Eva thinks about Zoref.
To highlight the utterly alien nature of the unknown life-force, the regular Barry Gray score was replaced by abstract electronic compositions drawn from the music library. Those featured were 'Cosmic Sounds No. 1', 'Cosmic Sounds No. 2' and 'Cosmic Sounds No. 3' by Georges Teperino and 'Videotronic No. 3' by Cecil Leuter. Another synthesised music track, 'The Latest Fashion' by Giampiero Boneschi, was used as the piped music heard throughout the Solarium scenes.
Novelisation
The episode was adapted in the third Year One Space: 1999 novel The Space Guardians by Brian Ball, published in 1975. Ball's adaptation is true to the story, but some liberties are taken: Suffering from a bout of depression, Koenig has become a recluse after his experience on Zenno. He is seen convalescing in his quarters and experiencing migraine when thinking of his lost love Vana. This crisis eventually forces him out of his fugue state; The approaching entity does not employ a paralysing force in the adaptation. The Alphans attempt to blast it with nuclear missiles before it joins with the unfortunate Zoref; While harbouring the entity, Zoref undergoes a gradual physical transformation into a shambling, thick-skulled humanoid creature.
