Ladies in retirement (1941)

In this taut, creepy melodrama, a housemaid works as the companion of an aging, retired British actress. One day the maid (Ida Lupino) is visited by her two looney half sisters. The actress finds the slightly mad sisters intolerable and demands that they leave. Unfortunately, the maid realizes that if the sisters are sent away they will end up involuntarily committed to an insane asylum and so the maid kills the actress and lets the sisters stay. Things go well until a suspicious relative shows up and starts to investigate.