The All Her Fault Book Ends With 2 Major Twists

Peacock’s new, star-studded thriller may be called All Her Fault; however, in the Andrea Mara book it’s based on, the truth is anything but.

In the new limited series (out Nov. 6), Sarah Snook and Dakota Fanning play moms whose lives intersect in the wake of a tragic crime. And if the 2021 novel is any indication, you definitely won’t see the conclusion coming.

For a peek ahead, here’s the All Her Fault book ending and plot summary.

A Mysterious Disappearance

The novel (set in the suburbs of Dublin, but moved to Chicago for the series) begins with an accomplished lawyer named Marissa attempting to pick up her son, Milo, from a playdate. She set it up via text with her new mom friend, Jenny, but is disturbed to learn that she was given a fake address. In fact, she was never texting with Jenny at all.

It turns out that Jenny’s nanny, Carrie, picked up Milo from school and kidnapped him. The lack of a ransom note leaves Marissa and her community unsure of Carrie’s motive.

Milo Is Found

Following a week-long investigation, Milo is found safe in an empty car. The 4-year-old recalls being treated well in captivity. Though curiously, Carrie dyed his blond hair brown.

Shortly after Milo’s return, Carrie is found dead in the house where she’d kept him. Her boyfriend, Kyle, is killed, too, followed by her father and Colin, Marissa’s friend and business partner, who had briefly dated Carrie.

Soon, a smoking gun: Milo recalls that the masked man who removed him from the house and placed him in the car called him “Milo Mouse,” a nickname that only his dad, Peter, ever used. Marissa confronts Peter about this, and he admits to having done it.

Peter had previously encountered Carrie at the playground, where she recognized him as part of the couple with whom she’d been in a car accident four years earlier. She lost her newborn baby in the accident, and Peter thought that Carrie had wanted to take Milo to replace him.

Carrie becomes set on getting close to Milo by becoming a nanny for one of his classmates and dating Colin to obtain information about Marissa’s family. She planned to take Milo with the help of her dad and boyfriend, and raise him as her own. But once Peter figured out where Carrie was keeping Milo, he went to the house to retrieve his son — and killed Carrie.

When Carrie’s dad, Rob, learned she was dead, he demanded money from Peter or else he’d report him to the police. Peter sent Colin with the funds, blackmailing him because he’d been stealing from clients. But Rob shot Colin, after which Peter shot Rob. It’s later suggested that Rob likely killed Kyle for attempting to stop the kidnapping plot.

There’s Yet Another Twist

It’s... a lot! But take a breather, because none of this beats the most shocking reveal of all. Carrie wasn’t just trying to take Milo because she lost her child. He was, in fact, her child!

Marissa realizes that Peter, recalling the playground encounter, said Carrie tried talking to Milo about seeing days as colors — believing it to be genetic synesthesia, as Milo talked about seeing things the same way. This prompts Peter to admit that, in the aftermath of the accident that left both Carrie and Marissa unconscious, their baby died on impact, but Carrie’s was still alive. So, he swapped the children from their car seats and pretended Carrie’s little one — like the real Milo, a newborn — was their own.

Naturally, Marissa is horrified to learn the extent of Peter’s crimes. But Peter convinces her not to report it to the police, pointing out that Milo could be taken away.

She reluctantly agrees. Six months later, another shock: Peter dies on vacation in Spain after accidentally consuming shellfish — to which he was deathly allergic — in a stock cube purchased by Marissa. She couldn’t find his EpiPen, a news report reads.

Whether Marissa played an intentional role in Peter’s death is certainly up to interpretation. For example, she mentions Peter’s allergy multiple times in the book — signaling her acute awareness of it. And, in the final pages, Peter is described as a “stranger” to Marissa following his shocking and violent actions, and she’s nervous to be around him and wants to protect Milo from him.