Blanche Fury(1948)

Penniless governess Blanche Fullerton takes a job at the estate of her rich relations, the Fury family. To better her position in life, Blanche marries her dull cousin, Laurence Fury, with whom she has a daughter. But before long, boredom sets in, and Blanche begins a tempestuous romance with stableman Philip Thorn. Together, they hatch a murderous plan to gain control of the estate.