She has no name. Played by Bette Davis, the eponymous character of The Nanny (1965) is only referred by her title. In fact, when the movie flashbacks as she narrates a bad moment in her life, we're surprised to learn she had anything resembling a life outside of her job. Of course, given what we see from that flashback and what we hear, it's safe to assume her life was not a happy one.
The Nanny is a domestic, psychological thriller, a story in which buried secrets, shame, and guilt tear into a family. It's not too dissimilar from all those movies that arrived the 90s about a disturbed individual who ingratiates their way into a vulnerable family/couple/individual and threatens to destroy them - Sleeping with the Enemy, The Hand that Rocks the Cradle, The Good Son, Single White Female, etc. Not surprisingly, The Nanny is better than all of them, crafting genuine suspense instead of hackneyed Hollywood cheese.
Young Joey Fane (William Dix) returns after two years at a special school for problematic boys. His younger sister Susy died, and Joey was blamed for accidentally killing her. His strict father Bill (James Villiers) wants him to straighten out while his mother Virginia (Wendy Craig) is an emotional wreck who resents Joey. Nanny tries to dote on him, but he rejects her offers, claiming she's the one who killed Susy and convinced she really wants to kill him.
But Nanny is played by Bette Davis. She doesn't have to do or say anything outwardly wicked to seem ominous. Her eyes see everything, and her take-it-in-stride responses to Joey's cruel behavior is enough to make you wonder what she really is thinking. Why does she put up with this nasty boy, his head case mother, and his domineering father?
Based on a book by Marryam Modell and directed by Seth Holt, The Nanny is a tight thriller, confined mostly to the building where the Fane family lives, and as the movie goes on, the home becomes more and more confining and twisted, a place of shadows and dark hallways. It's about as far from cozy as you can get, which is appropriate for the movie. Instead of a family coming together after an awful tragedy, the members grow further and further apart. The only person holding them together is the one who is ultimately the biggest threat to them.