What is this movie about ?

"Drama is life with the dull bits cut out. " Alfred Hitchcock

This movie is about a policeman, John Ferguson (Scottie) who suffers from acrophobia (This is, "extreme or irrational fear to heights").
At the beginning of the movie, Scottie runs with another policeman over some towers of San Francisco. They are pursuing a thief.
One of those policemen jumps from one tower to another and continues the pursuit. The second policeman, Scottie, slips down a steep roof and ends up hanging from a gutter.
When the other policeman realizes that Scottie is in trouble, he goes back and tries to give Scottie his hand in order to prevent him from falling. Scottie, tries hard to reach the policeman's hand but he fails and finally is the policeman who tries to save him from death the one who falls from the top of the tower and dies. After this dramatic event, Scottie quits his job as policeman.

Some time after this event, Scottie is called by Gavin Elster.
Elster's wife has had an unusual behaviour and he asks Scottie to follow her. He tells Scottie that his wife (Madeleine) is probably possessed by a dead person.
Scottie, who does not believe in those things, asks Elster to take his wife to the doctor, but Elster refuses and says that he prefers Scottie to follow her. Since Elster is an old friend, Scottie finally accepts.
Scottie sees Madeleine at Elster's Restaurant for the first time and immediately he falls in love with her.

During the following days, Scottie begins following Madeleine and he becomes really worried about the way she behaves. She visits a museum and gazes at the portrait of a lady called Carlotta Valdes for a long time. After that, she goes to the grave of this woman to let her flowers.

Scottie asks himself who the woman in the portrait is, and what does she has to do with Madeleine.
Elster reveals that Carlotta Valdes is Madeleine's great grand mother.After knowing this, Scottie becomes obssessed with Madeleine and keeps her under careful surveillance. Furthermore, he saves her from committing suicide.
After this event they become closer and she tells Scottie that there is someone inside her that tells her that she must die. At that moment she also mentions the tower of a church.

Trying to do his best, Scottie takes Madeleine to a place that resembles the place that she describes. This place is an old Spanish mission. When they arrive in the mission, Madeleine escapes and goes upstairs in the tower of its church. Scottie, while going upstairs in order to save her, feels the vertigo again, in the same way as he felt it when hanging from the gutter. The vertigo makes Scottie fail at saving Madeleine.

Devastated and feeling a great guilt, Scottie is hospitalized.But one day, after leaving the hospital, he sees a woman that resembles Madeleine. He knows that Madeleine is dead because he saw her, but could she be Madeleine ? That is what Scottie is about to find out.