Lady with a Black Umbrella

Signet Regency, 1989, ISBN 0-451-16222-6

Daisy Morrison, staying at an inn one night on her way to London, sees a gentleman being attacked by ruffians in the yard below. She charges down in her nightgown, wielding her father's large black umbrella, and routs Viscount Kincade's assailants. She then--after the viscount's departure--pays his bill and the chambermaid with whom he had spent the night. Kincade is not amused when he learns the truth! The book is a farce.

Lady with a Black Umbrella by Mary Balogh