The Undoing follows Grace Fraser (Nicole Kidman) and Jonathan Fraser (Hugh Grant), who live a privileged life in Manhattan with their son, Henry (Noah Jupe). Most of The Undoing follows the court case against Jonathan, revealing secrets.
Although The Undoing tried to throw a few red herrings at its audience throughout its six episodes, the identity of the killer was not a huge surprise. They were always the most suspicious characters.
The Undoing revealed that Jonathan killed Elena. The odds were in favor of Jonathan being the killer. Even when trying to convince his audience that Grace or Henry could have killed Elena, it was always clear that it was him.
Once Jonathan is formally charged with the murder, Grace learns shocking information from her mother. Grace, a trained psychologist, eventually realizes that her husband may have a narcissistic disorder in The Undoing.
During the entirety of the case in The Undoing, Jonathan is horrified at the idea that someone believes that he murdered Elena. He cries during a television interview and suggests his son may have committed the murder.
Most likely, Jonathan was just obsessed with his image and the power that came with it. Once he’s run out of lies and excuses in the ending of The Undoing, Jonathan almost has a break from reality when he walks away from jumping off a bridge.