The Nanny(1965)

Nanny, a London family's live-in maid, brings morbid 10-year-old Joey back from the psychiatric ward he's been in for two years, since the death of his younger sister. Joey refuses to eat any food Nanny's prepared or take a bath with her in the room. He also demands to sleep in a room with a lock. Joey's parents -- workaholic Bill and neurotic Virgie -- are sure Joey is disturbed, but he may have good reason to be terrified of Nanny.