‘All Her Fault’: The Biggest Differences Between the Show & Book

[WARNING: This post contains MAJOR spoilers from All Her Fault, the show and the book.]

Peacock’s twisty new thriller, All Her Fault, was based on the 2021 novel of the same name by Andrea Mara. However, there are several pivotal differences between the book and the adaptation.

The premise, of course, is the same: Marissa Irvine (Sarah Snook) goes to pick up her son Milo (Duke McCloud) from a playdate at Jenny Kaminski’s (Dakota Fanning), only to find out the playdate never happened and Milo had been kidnapped by Carrie Finch (Sophia Lillis), the Kaminskis’ nanny.

The main twist (Carrie’s reason for the kidnapping) is the same in the book and the show. Marissa, her husband, Peter (Jake Lacy), and a newborn Milo had been involved in a car accident while leaving the hospital. Carrie and her own newborn baby were in the other car. When Peter realized his own baby had died in the crash, but the baby in the other car had survived, he switched them, without telling Marissa, and he and his wife raised Carrie’s baby as their own.

For years, Carrie was under the impression that her baby died in the accident, but she eventually crosses paths with the Irvines again and figures out that she and Milo both have a sensory condition called synesthesia, which is genetic. This leads her to realize that he is really her son, setting her elaborate kidnapping plan in motion.

Related

'All Her Fault' Ending: Answers to All the Show's Burning Questions

But there are several other major storylines that changed in the show from the book, and we’ve outlined the biggest ones below!

The Irvine siblings

Perhaps the biggest difference from book to show was that of Peter Irvine’s siblings, Brian Irvine (Daniel Monks) and Lia Irvine (Abby Elliott). For starters, in the book, Lia was not a major character in the book. She lived in New York, far away from the Irvines in Dublin (another difference, as the show takes place in Chicago), and only arrived toward the end of the story as a support system for her family.

In the show, though, Lia plays a major role. She was on the scene in the Irvine house from the jump after Milo’s disappearance. Her complicated relationship with Peter, due to her past as a drug addict, is heavily highlighted. Plus, she’s in a secret relationship with Marissa’s business partner, Colin (Jay Ellis), whom she only went on one date with “a million years ago” in the book.

Sarah Enticknap / Peacock

Meanwhile, Brian had a larger role in the book, but his character in the show is completely different. One of the major storylines in the show involves the Irvine siblings’ power dynamic, stemming from an accident that took place when they were children, which left Brian disabled (in the book, he is able-bodied). Lia is under the impression that she caused the accident, leading to her downward spiral and pill addiction. Because of Brian’s physical disability and Lia’s issues, they often have to rely on their older brother, and he likes being in the power position.

One of the most pivotal scenes in the entire show is a showdown between the Irvine siblings in Marissa and Peter’s living room, but this is not part of the book at all. In fact, the family history and dynamic is barely explored in the novel. Yes, Brian lives on the Irvine compound, but he manages just fine on his own. Instead, his book storyline is more of a red herring and focused on his secret relationship with a woman amid his journey to become more independent.

The manner of deaths

There were several deaths in both the book and show, but the events of almost all of them were different. In the show, Carrie’s dad, Rob (Erroll Shand), kills her boyfriend, Kyle (Dominic Masterson), because police had figured out his connection to Carrie and plastered his face on the news. Rob, a bookie and criminal in his own right, is not happy that Kyle’s identity had been figured out, so he takes it upon himself to kill him.

Then, Rob dies after meeting up with Peter to get the ransom money he called for. Peter shoots and kills Rob instead of exchanging the money. Peter also shoots and kills Carrie when she shows up at his home with a gun, charging at her and turning the weapon on her instead. Meanwhile, Carrie is the one who kills Colin after she accidentally pulls the trigger before being shot herself. Finally, Marissa kills Peter by eating soy, which he’s deathly allergic to, at Colin’s funeral and then kissing him … after conveniently making sure he only had an expired EpiPen in his pocket.

Sarah Enticknap / Peacock

On the other hand, in the book, Rob is suspected of killing Kyle, but his exact motives aren’t laid out. Meanwhile, Peter killed Carrie in the book by smothering her with a pillow at her home, not shooting her. Then, Peter was worried Rob would want to avenge his daughter’s death and kill him, so he sent Colin to meet Rob with the ransom money in his place. His suspicions were right, as Rob ended up killing Colin, thinking he was Peter. The killer and motive for Rob’s death is the same in the book as the show, with Peter then showing up and murdering him amid the ransom demands.

Finally, in the book, Peter was allergic to shellfish, not soy, and Marissa killed him by making sure he ate shellfish while they were on vacation in Spain. It’s not specified whether Jenny (Dakota Fanning) was aware of what she was going to do, whereas in the show, Marissa shares her plan with Jenny.

The detective’s backstory

For starters, the lead detective in the book is a woman, while on the show, Detective Alcaras is a man played by Michael Peña. The show dives into Alcaras’ personal life, which does not happen in the book.

Almost an entire episode is devoted to getting to know Alcaras better, particularly in regards to his son, who has special needs. Alcaras and his wife are desperate to get their son into a special facility that only has one spot left.  He places a call to someone who may be able to help, and is met with a blackmail demand. The facility can make it happen that the final spot goes to Alcaras’ son … if he helps get rid of evidence that could result in the director of the facility’s son facing legal trouble.

Sarah Enticknap / Peacock

Alacaras is committed to his job and doing the right thing, but his son matters more. He ends up tossing the evidence, and his son earns the final spot in the facility.

This ends up playing a role in the greater storyline, as it gives insight into why Alcaras let Marissa off the hook, even though he realized that she intentionally caused Peter’s death. As he sees it, sometimes wrong things might have to be done for the greater good.

The cause of Jenny’s marriage issues

There is some insight into Jenny’s personal life in the show, which ultimately leads to her asking her husband for a divorce. Their problems stem from him not wanting to step up as a father and getting annoyed at her when she has to work, leaving him in charge of their son.

Narelle Portanier/PEACOCK

This is similar in the book, where it’s specified that Jenny earning a higher salary than Richie after a promotion at work is a big source of contention. However, Richie’s meddling mother, Adeline, also played a part in the marriage issues. Adeline is not even a character in the show, but in the book, she secretly sent Richie letters insinuating that Jenny was having an affair with a man at work. It seemed to be her mission to make Jenny’s life miserable.

In the end, Richie became fed up with his mother, and he and Jenny appeared to be on the path towards reconciliation, rather than divorce, like in the show.

Carrie’s mother

The All Her Fault book is told from the points of view of different characters, including Carrie’s estranged mother, Irene Murphy. Although she and Carrie haven’t seen each other for years, she wants to capitalize on her daughter being in the spotlight, so she reaches out to journalists to exploit Carrie by conducting paid interviews.

In the show, Carrie’s mother is played by Caroline Brazier, but she has a much smaller role. Yes, she’s questioned by police amid the investigation, and viewers get to see her complicated past with Carrie, but she isn’t a main character, as she is in the book.

All Her Fault, All Episodes, Streaming Now, Peacock