In London in June 1897, a young mouse named Olivia Flaversham is celebrating her birthday with her toymaker father, Hiram. Suddenly, a bat with a crippled wing and a peg leg bursts into the Flaversham’s workshop, kidnapping Hiram. Olivia searches to find the famed Great Mouse Detective named Basil of Baker Street, but gets lost. A surgeon named Dr. David Q. Dawson, who has just returned from a lengthy service of the Mouse Queen’s 66th Regiment in Afghanistan, meets Olivia, and escorts her to Basil’s residence. Upon their arrival, Basil is initially indifferent, but when Olivia mentions the peg-legged bat that kidnapped her father, Basil realizes that Olivia saw Fidget, a henchman of Professor Ratigan, a villain that Basil has attempted to arrest for years. It is then revealed that Ratigan kidnapped Hiram to create a clockwork robot, which mimics the Queen of the Mice so that Ratigan can rule England. Hiram initially refuses to participate in the scheme, but capitulates when Ratigan threatens to harm Olivia. Ratigan then announces his plans to kill the Queen and become “supreme ruler of all mousedom” to his henchmen.