When a wealthy bachelor dies at the autumn ball, a young lady takes on the improper role of detective in a comedy full of action.

The dynamic Beatrice Steele is not exactly a "proper young lady": she is terrible at embroidery, lacks musical skills, and her painting is so bad it frightens people. However, she follows crimes in the newspapers with great passion. Otherwise, she lives a perfectly pleasant life with her matchmaking mother, her prankster father, and her two younger sisters – the beautiful Louisa and the colorless Mary.

At the ball, Beatrice tries to be on her best behavior. Suddenly, in the middle of a minuet, the sought-after bachelor Edmund Croaksworth drops dead. Outside, a storm rages and the night turns into a frenzy of panic, fear, and betrayal, as it becomes clear that everyone is trapped with a killer. Beatrice must overcome decorum and propriety to bring justice – before another murder occurs.