'All Her Fault' Ending, Explained: Breaking Down the Twists in the Peacock Series

In the opening moments of All Her Fault, Chicago businesswoman Marissa Irvine (Sarah Snook) goes to pick up her 5-year-old son, Milo, from a playdate—only to find out he was never there, and the mom she thought she’d been texting with, Jenny Kaminski (Dakota Fanning), has no idea what she’s talking about. That nightmare scenario kicks off a frantic search for the young boy, unearthing more than a few shocking secrets.

Based on the thriller novel of the same name by Andrea Mara, All Her Fault has surprises at every turn as it unravels the mystery of who took Milo and why. The must-watch series also tackles the expectations put upon working mothers, as the media and others around Marissa and Jenny—whose nanny, Carrie Finch (Sophia Lillis), quickly becomes a prime suspect in the case—question whether what happened is, well, all their fault.

The twisty Peacock thriller, which premiered on November 6, takes some unexpected turns throughout its eight episodes. But how does it all end? Read on as we break down all the big reveals at the end of All Her Fault.

Why does Carrie kidnap Milo in 'All Her Fault?'

Early on, it’s revealed that Carrie has been fixating on Milo (Duke McCloud), even going as far as to create a fake identity and get a job with Jenny as a nanny to her son, Jacob (Tayden Jax Ryan), to get close to him. So it’s never a question of if Carrie abducted Milo—it’s why.

By the end of the series, we have a motive. Carrie, whose real name is Josephine “Josie” Murphy, was pregnant with her own son as a teenager, but the baby was tragically killed in a car crash as they were leaving the hospital. Carrie becomes convinced that Milo is actually her son, and plots with her ex-boyfriend and baby’s father, Kyle Smit (Dominic Masterson), recently released from prison after serving time on a drug-trafficking charge, and her bookie dad, Rob Murphy (Erroll Shand), to abduct him. Marissa had never coordinated a playdate with Jenny before, so she didn’t realize she wasn’t actually texting with Jenny, and the address she was given for pickup wasn’t Jenny’s home. And because Carrie was already a familiar face to Milo—she and Jacob would stop for milkshakes with Milo and his nanny, Ana (Kartiah Vergara), regularly after school—he wasn’t alarmed when she picked him up from school.

But is Milo actually Carrie’s son in 'All Her Fault?'

Yes. When Carrie/Josie tagged along with her father to confront Marissa’s friend and business partner, Colin Dobbs (Jay Ellis), a gambling addict who had relapsed and owed him money, she sees and then briefly speaks with Milo, which is what sparks her plot to get him back.

It’s eventually revealed that Marissa, her husband, Peter (Jake Lacy), and their newborn were involved in that same car wreck as Carrie six years ago—in fact, Marissa and Carrie gave birth to their sons on the same day. In the aftermath of the accident, while the two women were both unconscious, Peter realized that their son had been killed and, thinking Carrie had also perished, switched the babies. Marissa, meanwhile, believed the other mother in the crash had died by suicide after the death of her child, and so it didn’t occur to her that the accident could have had anything to do with Milo’s present-day disappearance.

Detective Alcaras (Michael Peña), one of the cops investigating Milo’s disappearance, also comes to believe Carrie and Milo are related once he learns that they both have synesthesia, a neurological condition in which sensory information can overlap (such as words having tastes or sounds having colors). It’s apparently rare, as he discovers while working on the case, and is often inherited.

What happens to Milo in 'All Her Fault?'

After Carrie collects Milo from school (telling him they’re going on “vacation”), she dyes his distinctive blonde hair darker and hides out with him and Kyle at a rented lake house. But when the cops release a photo of Kyle as a potential suspect in Milo’s disappearance—captured from surveillance footage at the Chicago Marathon, where Carrie had arranged for Kyle to see Milo for himself—Rob considers him burned and kills him, dumping his body in the lake.

Carrie and Milo then move to a motel, but while Carrie is out getting Milo a cake for his 6th birthday, Rob meets with Peter for a ransom handoff, which he coordinated without telling Marissa or the detectives. Rob remarks that his daughter thinks Milo is her son, and then, when his back is turned, Peter strikes him with a lamp, killing him. He then finds Milo hiding in a closet and places him in the trunk of a car that he leaves near a police station, ensuring that he’ll be found.

This all means Milo is returned home to his parents unharmed. However, it doesn't stop the ripple effects that were sparked by his disappearance, which go far beyond the vitriol thrown around in the court of public opinion. (Not only did the tabloids speculate that Marissa had fabricated the incident to try to get money to save her wealth management firm, but they also alleged that Jenny employed a nanny because she was more concerned about partying than taking care of her own son.)

What happens to Carrie at the end of 'All Her Fault?'

After Milo is safely returned, Carrie goes to the Irvines’s home with a gun. After Colin attempts to get the gun away from her, she accidentally shoots and kills him in the struggle. She then tells Marissa that she hasn’t come to take Milo again, but to reveal her true identity as Josephine Murphy, and to warn her about Peter.

As she’s about to play a recording from a cell phone that is presumably to show Peter’s true colors, Peter tackles her, and she’s shot and killed with her own gun. Peter swears it was in self-defense, but Marissa fears he was trying to prevent Carrie from sharing what she knew about him.

Marissa does listen to the recording, which documents what happened in the motel room. Peter then confesses that he switched their dead son for Carrie’s living one the night of the car wreck, and Marissa finally understands the full picture of who she’s married and what he’s capable of. She’s afraid of what he’ll do if she goes to the police, and that Milo could be taken away if the truth gets out.

What happens to Peter at the end of 'All Her Fault?'

Milo’s disappearance unlocks an entire host of Peter Irvine’s secrets, not just limited to what he did on the night of that car crash six years earlier. It also comes out that Peter lied about his involvement in a childhood accident that left his younger brother, Brian (Daniel Monks), disabled, and let their sister, Lia (Abby Elliott), believe it was her fault—permanently changing their relationship and making her feel the guilt of it for all these years. He also lied to his brother about not being a candidate for a spinal surgery that could have improved his quality of life, because he enjoyed the control he got from being needed by his siblings.

A few weeks after the standoff at the house, Marissa takes matters into her own hands. When everyone gathers together for Colin’s funeral, Peter suffers a severe allergic reaction after Marissa kisses him. Marissa, who is well aware of Peter’s soy allergy, had seemingly eaten something without checking the dietary labels. Though she is normally very careful to check the ingredients of everything, she claims to have forgotten in this instance, due to how stretched she’s been mentally. Peter goes to grab an EpiPen from his jacket, but it’s expired, which is, again, something Marissa has always managed diligently. She sends Lia to call 911 and grab an emergency kit from their car, but it’s not in its usual place, and it’ll take time for the ambulance to arrive.

A flashback reveals that she orchestrated everything, grabbing an expired pen from a home disposal container and removing the kit from the car. As Peter dies, he does so knowing Marissa did this on purpose.

How does 'All Her Fault' end?

At the end of the final episode, Detective Alcaras and his partner investigate the circumstances around Peter’s death. They ask Lia about the food labels at the wake and if she saw Marissa check them before eating. Remembering how Peter treated her and Brian, Lia chooses to cover for her and implies that it was an accident.

Later, he goes to Marissa and reveals what he knows about synesthesia, the condition that Carrie had, and, because it can be inherited, Milo does too. He then explains that he knows what Peter did, and that he’s “fine” with the case being closed now. The series then ends with Marissa and Jenny sharing a calm moment together while their sons play.