Sex. Murder. Blackmail. There's a first time for everything.

Desperate to be free from her drunken, unloving mother Diane, the beautiful, scheming young Mini seduces her stepfather Martin and soon convinces him to join her in a sadistic scheme to have Diane declared insane. But their conspiracy soon escalates to murder and when John Garson, a young detective starts investigating, Martin and Mini begin to turn on each other.