The script began with a description of the domes that make up the Frost Line Command Centre: "Deep snow surrounds the plexiglass domes ... From the large central dome acting as a hub, avenues run off in eight directions. At the end of each spoke at varying distances from the centre are smaller domes. Each dome is airtight and serviced by an artificial atmosphere from an air-conditioning dome." Chris Bentley, author of "The Complete Gerry Anderson: The Authorised Episode Guide", suggests that some of this detail was lost in the transition from script to screen. On arrival at Red Deer Base, Scarlet and Green were described as wearing "space-type helmets"; in the episode as filmed, they wear breathing masks and their standard Spectrum caps.