The Doctor’s investigations take him first to the sewers, where there are indeed giant rats on the loose, and then to the Palace Theatre, where a stage magician, Li H’sen Chang, is procuring young girls for his master, the ancient Chinese god Weng-Chiang. Weng-Chiang is in fact Magnus Greel, a war criminal from the 51st Century. The journey back through time has disrupted his molecular structure and he now needs to feed on the life force of others - hence his use for the young girls. He has come to London to retrieve his lost time cabinet, which is in the possession of Litefoot. Infiltrating Litefoot’s home with Chang’s ventriloquist doll Mr Sin - a computerised homonculus with the brain of a pig - he retrieves the cabinet and prepares to travel back to his own time.