A former English boxing champion, Billy Baker, arrives in America with a kangaroo with an unusual talent for boxing. Needing to support himself, he reluctantly joins up with a small time talent agent featuring the kangaroo, Matilda (who's a male kangaroo despite the feminine name) as a carnival act. But when the world heavyweight boxing champion, Lee Dockerty, offers to take Matilda on at the carnival to impress a girlfriend, and Matilda KO's Dockerty into the middle of next week with a single punch, Billy and his marsupial friend are catapulted into the big time, with Matilda now headlining main boxing events, and soon ready to challenge Dockerty for his championship title. This attracts the notice of a mob boss who wants control of Matilda and his growing fame and fortune, and an activist determined to see Billy and Bernie stopped for promoting cruelty to animals. It will take all of Bernie's wits, Billy's wisdom, and Matilda's punching speed and power to get themselves all through in one piece, as Dockerty prepares to defend his title in the ring!