Roddy St. James is a decidedly upper crust pet rat who makes his home in a posh Kensington flat. When a common sewer rat named Sid comes spewing out of the sink and decides to stay, especially as England are playing Germany in the World Cup final, Roddy schemes to get rid of Sid by luring him into the "jacuzzi", which is actually the toilet. Sid may be an ignorant slob, but being a sewer rat, he knows his plumbing. He plays along and instead pushes Roddy in and flushes him away into the sewer. There, Roddy meets Rita Malone, an enterprising scavenger rat who works the drains in her faithful boat, the Jammy Dodger. Rita does not like Roddy initially, but ends up taking him along as The Toad sends his henchmen, Spike and Whitey, after her because she had stolen back her father's prized ruby a long time ago. The Toad despises all rodents to the point of hateful obsession, blaming rats for his fall from grace (he was once Prince Charles' pet). He decides to have them frozen with liquid nitrogen. However, The Toad's plan fails. Worse, during their escape, Rita takes a unique electrical cable. The cable is required to control the Floodgates. The Toad's evil plan is to open the gates during halftime of the World Cup, drowning the rats and their underground city in sewage. He can then use the depopulated city as a home for millions of his own tadpole offspring.