A Kiss Before Dying

Jonathan killed Dorothy because she became pregnant, which threatened his plan to marry into the Carlsson fortune undetected. He had been secretly dating her while planning to assume a new identity and infiltrate her family for financial gain. The pregnancy would have exposed their relationship and ruined his scheme, so he pushed her off the City Hall rooftop to eliminate the problem.

Earlier in the film, Dorothy doodles wedding images during class, showing she dreamed of marriage, unaware her boyfriend was planning to murder her.

The real Jay Faraday was a drifter whose parents had died on Korean Air Lines Flight 007. Jonathan discovered this information and assumed the dead man's identity to create a clean backstory for himself. This allowed him to reinvent himself as Jay Faraday and approach Ellen Carlsson without the baggage of his true identity.

Jonathan assumed the identity of Jay Faraday to escape his past and insert himself into the Carlsson family. After killing Dorothy, he needed a new persona to pursue his original plan of marrying into the wealthy Carlsson family. By becoming Jay Faraday, he could approach Dorothy's twin sister Ellen with a believable, guilt-free history.

The opening scene shows a young boy watching trains near the Carlsson refinery, hinting at Jonathan's long-standing obsession with the wealthy family.

Tommy Roussell was strangled by Jonathan Corliss. When Ellen investigated Dorothy's death and contacted Tommy, he began searching for a photo of Dorothy's other boyfriend in an old yearbook. Jonathan stalked Ellen, discovered Tommy was close to identifying him, and killed Tommy before he could reveal the information. Jonathan then forged a suicide note on Tommy's computer to make it look like a confession.

Ellen believed Tommy was Dorothy's killer because Jonathan forged a suicide note on Tommy's computer confessing to the murder. Jonathan staged the scene to frame Tommy, who was already a former boyfriend of Dorothy. Ellen had no reason to suspect the note was fabricated, so she accepted that Tommy had killed her sister and moved on with her life.

Patricia was strangled by Jonathan in her hotel room. She had remembered the identity of Dorothy's former boyfriend and planned to visit Ellen with the information. Jonathan intercepted her call and killed her to prevent her from revealing what she knew. He then dismembered her body and dumped it in the East River, maintaining the appearance of a normal evening with Ellen.

Ellen became suspicious of Jay after he was recognized as Jonathan Corliss at a bar. An acquaintance called him by his real name and Jay attacked the man to deny it. This confrontation, combined with her growing unease, prompted Ellen to consult a university yearbook and confirm that Jay strongly resembled Jonathan Corliss, launching her investigation into his true identity.

At Jonathan's mother's house in Pittsburgh, Ellen discovered a suitcase filled with newspaper clippings about the Carlsson family. She also found Dorothy's engraved lighter, which Jonathan had stolen from the murder scene. The evidence confirmed her suspicions that Jonathan had been obsessed with the Carlsson family long before meeting Dorothy.

Jonathan was killed by a Carlsson Copper train at the exact spot where he had watched trains as a boy. While pursuing Ellen toward the train tracks, he was struck and killed by the locomotive. This poetic ending tied his childhood obsession with the Carlsson family's power to his ultimate demise by the very trains associated with their empire.

The opening scene establishes the boy watching trains pass by the Carlsson refinery, foreshadowing the final confrontation at that same location.

Dorothy's pregnancy threatened Jonathan's plan because it would have revealed their secret relationship and exposed his identity as Dorothy's boyfriend. His entire scheme depended on approaching Ellen Carlsson as Jay Faraday with no connection to Dorothy. A pregnancy would have made him the obvious suspect in Dorothy's death and destroyed his chance to marry into the fortune through Ellen.

Dorothy's lighter was an engraved lighter that belonged to her. Jonathan took it from her body after pushing her off the City Hall rooftop. The lighter became crucial evidence that Ellen later found among Jonathan's belongings at his mother's house, confirming his connection to Dorothy's murder.

Ellen discovered Jonathan's true identity through multiple steps. First, she recognized his resemblance to Jonathan Corliss in a yearbook after the bar confrontation. She then traveled to Pittsburgh, where Jonathan's mother claimed her son had died by suicide. Inside the home, Ellen found the suitcase of Carlsson clippings and Dorothy's lighter, finally confronting Jonathan with the truth.