Originally, the fifth story of season 18 was "Sealed Orders" by novelist Christopher Priest before being abandoned. Stephen Gallagher, who had written a number of radio plays, was called upon for a replacement, resulting in "Warriors' Gate". Commissioned in March 1980, this was Gallagher's first script for "Doctor Who" and had the working title "Dream Time". The story was influenced by a radio serial he had done in 1979 called "The Babylon Run" as well as the films of Jean Cocteau, such as "Orphée" (1950), in which mirrors provide a gateway into another world.