The Doctor and Mel Bush, looking for a swimming pool, land in Paradise Towers, a luxurious 22nd century high rise apartment building now fallen into disrepair and chaos. The building is divided between roaming gangs of young girls called Kangs, grouped in colour theme, and the Doctor and Mel encounter the Red Kangs. They have just discovered the death of the last Yellow Kang and are plotting how to attack the Blue Kangs. Elsewhere in the Towers, one of the Caretakers - who act as 'Judge Dredd' style policemen – is hunted down and killed by a robotic cleaner, which appeals to the sadistic Chief Caretaker when he overhears the death.