Possessed of a plot laden with time paradoxes, its resolution depended on contradicting another Fifth Doctor story, Time Crash, as well as the Nyssa story Logopolis, and even The Claws of Axos. In those earlier televised stories, materialising one TARDIS around another caused massive problems. Here, the Doctor solved the central plot issue by spending much of the fourth episode liberally materialising his TARDIS inside of itself multiple times, much to Nyssa's confusion and fear.