Scottie tails Madeleine to Fort Point (just beneath the Golden Gate Bridge), where she suddenly leaps into San Francisco Bay
Scottie rescues Madeleine and takes her to his home. The meeting is tense and leads to a strange intimacy between them, but Madeleine quickly slips out when Scottie receives a phone call.
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Madeleine suddenly runs into the church and up the bell tower. Scottie, halted on the steps by vertigo and paralyzing fear, watches as Madeleine plunges to her death.
After Scottie leaves, Judy has a flashback revealing that she was, in fact, the woman known as "Madeleine", but she is not Gavin's wife. Judy prepares to leave and writes a confession letter to Scottie explaining that she was an accomplice to the real Madeleine Elster's murder by Gavin, and how Gavin had taken advantage of Scottie's acrophobia. She rips up the letter and decides to continue the charade because of her love for Scottie.
Scottie remains obsessed by his memory of "Madeleine" and their similarities. He transforms an initially unwilling Judy until she once more resembles Madeleine. Judy agrees to change on the chance that they may finally find happiness together. But Scottie realizes the truth when Judy wears a unique necklace that he remembered from the portrait of Carlotta Valdes. Instead of dinner, Scottie insists on taking Judy to the Mission San Juan Bautista.
There, he reveals that he wants to re-enact the event that led to his madness, admitting that he now knows Madeleine and Judy are the same. Scottie forces her up the bell tower and angrily presses Judy to admit her deceit. Scottie reaches the top, conquering his acrophobia at last.
Judy confesses that Gavin had hired her to pose as a possessed Madeleine; Gavin faked the suicide by tossing the body of his already-murdered wife from the bell tower. Judy pleads to Scottie to forgive her because she loves him. The two embrace when a nun, in shadow, emerges from the trapdoor; startled, Judy steps backward and falls to her death. Scottie stands on the narrow ledge while the nun rings the mission bell.