Once upon a time an 11-year-old boy went to see the new Hitchcock movie.
He came home crying, and didn’t understand why.
Fifty-two years later, he thinks he knows.
Scotty Ferguson, recovering from the suicide of Madeline Elster, and from his guilt at having failed to prevent it, quite casually encounters on a San Francisco street Judy Barton, a young woman who, despite profound differences, reminds him eerily of Madeline.

Scotty can have Judy. She as much as tells him so: “To tell you the truth, I’ve been picked up before.” (Of course, we soon learn—though Scotty doesn’t—that she isn’t simply “easy”; she is actually Madeline, or the woman Scotty thinks of as Madeline, and she is still in love with Scotty, even as he is with her.)
So why does Scotty so desperately need to turn her (back) into Madeline before he can love her?
It is precisely because he can have Judy that he doesn’t want her. Among the many things Alfred Hitchcock’s Vertigo is about is the fantasies of men (underwear fetishism; necrophilia and its more common image, the defenseless sleeping woman; the confusion of dream women with real women; the seduction of a younger woman; the seduction of a stranger; dressing-up games, and undressing ones; voyeurism; playing doctor-and-patient, which Hitchcock had earlier assayed in Spellbound). And what men want is what they cannot have.