Trauma and Fear
The first scene in the film shows Scottie hanging from a rooftop experiencing extreme fear of heights, which leads to the death of the cop he is working with. After watching his coworker fall to his death, Scottie experiences a traumatic guilt response to the event, and decides to stop working as a detective because of his vertigo. Then, when he chases Madeleine to the bell tower at the mission, he gets stalled on the steps and is unable to save her from falling to her death. He takes responsibility for this event as well, and ends up in a sanatorium, filled with grief.
Fear and trauma are also represented by the character of Madeleine Elster, who is haunted by visions of a traumatic past. She is obsessed with a tragic ancestor, Carlotta Valdes, who went mad and committed suicide after being torn away from her child in the 19th century. Madeleine describes her descent into madness and depression in terrifying terms, haunted by visions and delusions. The film looks at the ways that trauma and fear distort our perceptions and cause us to lose our way in life.
Romance
Scottie is very skeptical of Gavin Elster's commission to follow his wife, insisting that the occult nature of Madeleine's visions are not to be believed. However, when he sees how beautiful Madeleine is, he grows more and more fascinated with her, and when he gets to know her, falls in love with her. She returns his love, but this is complicated by the fact that she is not Madeleine Elster at all, but someone that Gavin hired to pose as her.
The character of Midge was once engaged to Scottie, and still harbors feelings for him, growing jealous of his attraction to Madeleine. She represents unrequited love, a woman who thinks that by being devoted and protective of Scottie, she can win him. However, it turns out that she lacks the mystery, glamor, and ethereality of Madeleine, and ends up disappointed in love.
Obsession with the past
When Scottie meets Judy, whom he does not realize is actually the same person he knew as Madeleine, he becomes obsessive about turning his new girlfriend into the spitting image of Madeleine. He takes Judy to a department store and makes her try on dresses, yelling orders at the saleswomen like a maniac, trying to find the exact dress that Madeleine wore. He insists that Judy dye her hair and wear it exactly like Madeleine. By the end of the film, we see that Scottie is a man who has been completely obsessed with his traumatic past to the extent that he must recreate it in order to feel romantically fulfilled.
Additionally, when Scottie first meets "Madeleine," she alleges to be possessed by the past, drawn to the grave of a woman named Carlotta Valdes, and slowly merging her identity with that of the long-dead woman. Her visions are of histories with which she ought not to have any personal connection, but which haunt her waking life.
Performance
The ruse of Judy lies in the fact that she is, in fact, Madeleine, and that she was pretending to be Gavin Elster's wife the whole time. As such, her bewitching personality and temperament, with which Scottie fell so in love, was a performance all along. Judy was groomed to create a character of the troubled and unknowable wife, and it is this specter that so bewitches Scottie. Her identity and expression of her identity is something that Judy was hired to affect, and does not reflect her actual identity.
When Scottie meets Judy later, not realizing she is actually Madeleine, he forces her to perform once again, but she has reservations. She wants to be sure that Scottie is in love with the real her and not just the memory of Madeleine, but she soon realizes that only through her performance of Madeleine can she embark on a deep affair with Scottie.
Guilt
Scottie's vertigo is not a damning shortcoming in and of itself. Rather, it is an irrational fear. In fact, what makes his vertigo that much worse is the fact that it leads to deaths that could have been prevented. Scottie feels responsible for the death of the cop in the first scene, because his vertigo prevented him from being able to reach up and accept his help. Then later, he feels responsible for Madeleine's death, because his vertigo left him paralyzed on the steps of the bell tower, unable to run after her. This second time, his guilt lands him in a mental hospital, where he is nearly catatonic from a sense of grief and responsibility.
Femininity & Gender
Throughout the film, there are references to an "idealized" femininity as it is dictated by society. In the beginning of the film, Midge works as a designer of women's underwear, and Scottie observes a strapless bra that she has constructed in her studio. Midge's profession is a reflection of a society that wants women to look and present themselves in a certain way. Midge herself, however, is not up to Scottie's standards, as she behaves more like a mother than a lover. Madeleine, on the other hand, is the ideal image of elegant white American femininity, with bleached blond hair, elegant clothing, and an ethereal demeanor. It is this performance of femininity that Scottie falls in love with, and when he meets Judy, he is not only trying to transform her into Madeleine, but he is trying to integrate Madeleine's femininity into Judy's more tough and less high-class expression of gender. The differences between Judy and Madeleine are apparent because they have to do with their respective presentations of gender.
Death
Death is a recurring theme throughout the film. Scottie is racked by guilt about the memory of the death of a cop with whom he was working. Then Gavin Elster tells him that his wife, Madeleine, is also obsessed with death, particularly with the death of historical figure Carlotta Valdes. He also tells Scottie that he thinks Madeleine is at risk of committing suicide, and eventually stages this suicide. Death and its alternately fascinating and horrifying quality is a pervasive theme in the film.
