Hepburn plays the title role of Sylvia Scarlett. When her father Henry (Edmund Gwenn), while employed as a bookkeeper for a lace factory, is discovered to be an embezzler, they flee from the police, with Sylvia masquerading as a boy, to live as con artists. While on the run, they meet a dashing rogue, Jimmy Monkley (Grant), who partners with them in their con games.
This film features examples of:
- Con Man: Sylvia and Henry Scarlett are con artists, who are later joined by Jimmy Monkley.
- Just a Stupid Accent: Cary Grant's performance as Jimmy Monkley sees him incorporate a (rather unconvincing) Cockney accent.
- Missing Mom: Sylvia's mom dies at the beginning of the film.
- Sweet Polly Oliver: Sylvia masquerades as a boy, "Sylvester Scarlett", to evade the police.