Paradise Towers two elderly residents ("rezzies") live. Tilda and Tabby explain that all the able-bodied men left the Towers to fight a war, leaving behind only children and the elderly. The only other man still loose in the Towers is Pex, a would-be hero, who appoints himself Mel's guardian. At the Caretaker control centre, the Doctor meets the Chief Caretaker, who greets him as the Great Architect, designer of Paradise Towers, and then promptly calls for him to be killed The Doctor cites an imaginary rule from the Caretakers' manual, confusing them enough to make his escape. Mel and Pex meanwhile have
The Doctor (Doctor Who) the skin of the universe" as a means of contacting the Doctor and seeing whether it was safe to leave the parallel universe in which their planet, Gallifrey, had been left following the events of "The Day of the Doctor". This arc was penned by Steven Moffat, who has been exploring the significance of the Doctor's name in his episodes since 2006's "The Girl in the Fireplace", in which historical figure Madame de Pompadour reads the Doctor's mind and remarks, "Doctor who? It's more than just a secret, isn't it?" According to the in-vision commentary on the DVD release, David