War threatens London as Miss Pettigrew, a destitute governess, filches a client's card from her agency and presents herself at the door. A singer named Delysia Lafosse wants a social secretary as she seeks a West End role by sleeping with a feckless producer in the bed of Nick, a smarmy nightclub owner with whom she also dallies. She ignores Michael, her piano player, who loves her and has tickets for New York on the Queen Mary. Miss Pettigrew's job is to make sure Delysia gets the part. Over 24 hours, Miss Pettigrew is also called upon to help an ambitious and unfaithful fashion editor patch things up with her older fiancé, a lingerie designer. Has Miss Pettigrew found her calling?