Script editor Tony Barwick asked Alan Pattillo to write for "Captain Scarlet" because Pattillo had been a regular writer on "Thunderbirds". However, commitments to other projects meant that Pattillo was able to submit only one script for the new series. The castle setting was influenced by Gerry Anderson, who according to Pattillo "always liked to have a Scottish subject in his series." Pattillo's script called for technically-complex puppet scenes in which all ten marionettes playing conference delegates appear in the same shot. Due to the large number of guest characters the wardrobe department was required to make several new military uniforms.