The Servant (1963)
The aristocratic Tony moves to London and hires the servant Hugo Barrett for all services at home. Barrett seems to be a loyal and competent employee, but Tony's girlfriend Susan does not like him and asks Tony to send him away. When Barrett brings his sister Vera to work and live in the house, Tony has a brief hidden affair with her. After traveling with Susan for spending a couple of days in a friend's house outside London, the couple unexpectedly returns and finds Barrett and Vera, who are actually lovers, in Tony's room. They are fired and Susan breaks with Tony. Later, Tony meets Barrett alone in a pub and hires him back, and Barrett imposes his real dark intentions in the house, turning the table and switching position with his master.