The Gun in Betty Lou's Handbag (1992)

Betty Lou Perkins is a shy and meek librarian and nobody pay attention to her, in particular her husband, Alex. A criminal has been killed and she inadvertently find the murder gun. She wants to provide the trace to the police but no one listen to her, including her detective husband. In sheer frustration, she announces that she has committed the crime, which will cause troubles begin raising around her.