So It Turns out [SPOILER] Killed Elena in 'The Undoing'

*Spoiler Alert: Major spoilers for HBO's The Undoing ahead.*

HBO’s whodunit thriller The Undoing has officially concluded with a gripping finale that had fans guessing until the very last moments. 

Along with a resolution for the Fraser family, the tense final episode also answered the question that the show had been teasing all season long: Who killed Elena Alves?

For anyone who needs a brief recap, The Undoing is a psychological thriller in which a rich Manhattan couple’s comfortable life is shattered when the husband, Jonathan (Hugh Grant), becomes the prime suspect in the murder of Elena Alves (Matilda De Angelis), the mother of a boy at the same elite private school that their son attends. 

With the evidence pointing in several different directions, fans of the series had plenty of theories as to who the actual killer might be, but it turns out that very few of them guessed correctly. 

"The best you can do with a good book, if you want to dramatize it on screen, is do something else with it," series director Susanne Bier told Oprah magazine. "By doing that, you maintain the actual qualities of the book. But you create something that is possibly different and something in its own right."

In You Should Have Known, the book The Undoing is based on, Jonathan is responsible for the murder of Elena, and sends his wife Grace (Nicole Kidman, in the series) a letter in which he confesses to killing the mother-of-two to cover up their illicit affair.

But as it turns out, Susanne was only half telling the truth in suggesting to viewers that the on-screen dramatization would be different from You Should Have Known. The HBO series deviated from the book early on when Jonathan disappeared right after the murder was uncovered, but returned to the book’s plot line with the finale. 

In the end, we discover that it was Jonathan who killed Elena, as everyone had suspected back in Episode 1. 

The fact that Jonathan appeared to be the last person who saw Elena alive, was having an affair with her, and had lied about being fired from the hospital for sleeping with her all pointed to his guilt. 

But since this was an HBO series, many viewers felt that Jonathan being the killer was too simple an explanation, and given what director Susanne Bier had said, also too close to what had happened in the book.

But the writers decided to use this assumption and turn it on its head for the big reveal. All the clues that pointed to Jonathan were not ultimately a misdirect, as so many viewers had assumed. 

In the end, Jonathan was revealed to be not only Elena’s killer, but also a delusional narcissist who was so deep in his own lies that he himself seemed to believe them.

The entirety of The Undoing is now available to stream on HBO Max.