The Doctor and Mel visit Paradise Towers, a residential complex that promises a peaceful life to its residents. However, the establishment is far from what its name suggests: A conflict persists among the Kangs, humanesque multicolour beings who gather in opposing gangs based on which colour of the rainbow they bear; killer cleaning robots prowl the halls, and a secret in the complex's basement poses the greatest threat of all.

• Sylvester McCoy
• Bonnie Langford
• Richard Briers
• Clive Merrison
• Elizabeth Spriggs
• Brenda Bruce
• Judy Cornwell
• Howard Cooke