Taking a romantic tropical island week off with her boyfriend, an ambitious, decisive New York girl agrees to help her magazine out by covering a story on a neighbouring island. The only plane available is piloted by a laid-back heavy drinker with whom she shares a mutual dislike. But she has no choice and he can't refuse the money. When the plane crash-lands on an uninhabited island with little chance of rescue they both wish they had made other arrangements - at least to start with.

Roddy is a decidedly upper-crust "society mouse" who lives the life of a beloved pet in a posh Kensington flat. When a sewer rat named Sid comes spewing out of the sink and decides he's hit the jackpot, Roddy schemes to rid himself of the pest by luring him into the "whirlpool." Sid may be an ignorant slob, but he's no fool, so it is Roddy who winds up being flushed away into the bustling sewer world of Ratropolis. There Roddy meets Rita, an enterprising scavenger who works the sewers in her...