The racehorse Seabiscuit really existed, but this is not his true story -- this is a romance and centers on lovely Margaret O'Hara (Shirley Temple), an Irish lass who comes to cheer on her uncle Shawn O'Hara's (Barry Fitzgerald) horse during the big races and ends up falling in love with handsome jockey Ted Knowles (Lon McCallister). He asks for her hand, but she will only marry him if he gives up racing because she is still mourning the death of her brother, who was also a jockey. Ted is torn because he loves her, but he also wants to ride her uncle's horse Seabiscuit to victory. Her uncle convinces him to ride and then engineers matters so that his niece will still marry Ted. The film includes footage of the real Seabiscuit winning two different races during the 1940s.