RAI had agreed to co-finance the series, they had one stipulation: the programme would feature Italian talent. The characters that became Sandra Benes and Alan Carter were originally written as Italian nationals. Giancarlo Prete had been selected to play 'Captain Alfonso Catani', head of Reconnaissance. Shortly before production began, the Italian actor resigned, unwilling to commit to the twelve-month stay in England the role would require. (The part was quickly rewritten and awarded to Nick Tate.) Prete would be the first of four Italian guest artists chosen to fulfill the agreement. Sylvia Anderson selected him because he was not intimidated by series' star Martin Landau; Landau's ego, she recounts, was threatened by the Italian actors visiting for screen testing. The script contained several differences from the finished episode: (1) The music programme was written as a string quintet, of which Victor Bergman was a member—this was suggested by the presence of a violin in his quarters in the earlier episode "Alpha Child"; (2) Characters were to have spoken Mateo's given name 'Dan' throughout the segment; in the televised version, everyone only used his surname—including his girlfriend - the cast in fact pronounced it as "Matteo" sounds in Italian, i.e. "Matthew" ; (3) In a scene cut for time (but glimpsed in the 'This Episode' sequence), Bergman demonstrated his method to destroy the spirit: energy matching the spirit's wave pattern, but with reversed polarity. When in contact, the two opposing forces would cancel each other out. The animated energy shimmer seen when the spirit vanishes and is absorbed into Mateo's body was the only new visual effect seen in this instalment; the shots of Moonbase were library footage. The superimposed images of the spirit were practical effects, done 'in camera' with a half-silvered mirror. Novelisation The episode was adapted in the fifth Year One Space: 1999 novel Lunar Attack by John Rankine, published in 1975. References External links Space: 1999 - "The Troubled Spirit" - The Catacombs episode guide Space: 1999 - "The Troubled Spirit" - Moonbase Alpha's Space: 1999 page 1976 British television episodes Space: 1999 episodes