Now considered one of Hitchcock's finest, Vertigo stars Jimmy Stewart as Detective John Ferguson, a retired police officer who suffers from acrophobia and vertigo due to a fall he sustained on the job. He's hired to tail the unstable wife of a friend, played by Kim Novak. The wife attempts suicide and Stewart rescues her, only to fall for her.
When the woman finally succeeds in her next suicide attempt, Stewart is devastated by his inability to save her.
Later he sees a woman who looks almost just like her (Also played by Novak), and stalks her until he can manipulate a meeting, then a date, and finally starts taking over her life. Obsessed with the lost woman, he forces and manipulates the woman to change her hair and clothing to more resemble her doppelganger.
The twist is best left for the viewer to see, but it's classic Hitch. As is the harsh looks at the depths of human emotion - obsession and fear - that the director explores.
I wouldn't call this my favorite of the Hitchcock films, which is a shame. Jimmy Stewart is one of my favorite actors, but I still couldn't get caught up.