This computer-animated feature, directed by David Bowers and Sam Fell, explores a whole new world under London. A pet mouse named Roddy St. James (voiced by Hugh Jackman) is pretty much spoiled rotten. His owners live in a chic Kensington apartment, and Roddy has everything he could possibly want--except friends and a family. Everything changes for Roddy when his owners go away for a few days and their flat is invaded by a common rat, Sid (Shane Richie). Determined to reclaim his apartment and boot out the intruder, Roddy tries to talk Sid into enjoying the apartment "Jacuzzi," which is actually the toilet. But Sid is smarter than he looks, and soon Roddy is traveling down the pipes out of his sheltered life into a world that he never knew existed.

Emerged in Ratropolis and completely out of his element, Roddy is immediately caught up in an adventure. He meets Rita (Kate Winslet), a street-smart scavenger who travels the sewers by boat looking for riches that will help her care for her parents and multitude of siblings, and hires her to help him get above ground. But the villainous Toad (Ian McKellen) and his rodent henchmen, Spike (Andy Serkis) and Whitey (Bill Nighy), are constant problems. To make matters worse, the Toad is preparing to hatch an evil plot that promises to wipe out all the rats and mice dwelling underground, and he brings in his mercenary Parisian cousin Le Frog (Jean Reno) and his team to help get the job done. This comedy/adventure features first-class animation from the team that created WALLACE & GROMIT: THE CURSE OF THE WERE-RABBIT and is voiced by an all-star cast.