Peacock’s psychological thriller All Her Fault immediately starts with the gut-wrenching first moments after a mother discovers her child is missing.

Marissa Irvine (Sarah Snook) goes to pick up her 5-year-old son, Milo (Duke McCloud), from a playdate. When she arrives at the house, the person who opens the door is a stranger who has never heard of Milo. Marissa’s panic escalates when she calls Jenny Kaminski (Dakota Fanning), the mom who, Marissa thought, sent a text to set up the playdate between Milo and her son. But Jenny says she didn’t send the text. Plus, the tracker Marissa placed in Milo’s backpack is offline, and she realizes that someone has picked up her son from school. “I don’t know where my son is,” Marissa says with agonizing uncertainty.

While the search for Milo drives the storyline, “new questions lead to deep secrets, revealing cracks in the Irvines’ seemingly perfect world until everything is left shattered,” according to Peacock’s description of the drama.

Here’s what to know about the real events the show is based on and the twists and turns of the finale. Warning: spoilers ahead.

Is All Her Fault based on a true story?

The show is based on Andrea Mara’s 2021 novel, also entitled All Her Fault. It’s not based on a true story, but it’s inspired by real-life events experienced by Mara, who is an associate producer on the show. In June 2021, Mara shared in a video that the plot of the story is based on an experience she had in April 2015 when she went to pick up her daughter from a playdate. Nobody answered the door after a few tries, and she found herself standing outside an empty house.

"The panic only lasted for a few seconds, until a neighbor told me that the family had moved house a few weeks earlier and I was just working off an old address list," Mara said. "It all ended very quickly, much more quickly than it does for Marissa in the book."

The author also wrote about the incident in an essay for the Irish Independent in July 2022 and shared that she started to theorize that her daughter had been kidnapped after no one answered the door in those moments. Within five minutes, she reconnected with her daughter, but it made Mara think about how much trust parents put in other people when they drop their children off at school, playdates and parties.

"How do we decide what’s safe and not safe, when it comes to our kids?" the author wrote. "And why do parents today seem to worry more than ever?"

What happens to Milo?

Marissa and her husband, Peter (Jake Lacy), launch an urgent search for Milo. Detectives get involved, and Jenny’s nanny, Carrie Finch (Sophia Lillis), becomes the main suspect in Milo’s disappearance. While Milo is eventually returned home, Carrie, whose real name is Josephine Murphy, remains on the run.

Viewers learn that Carrie lost a newborn baby at age 16, leading to psychological instability and an obsession with Milo that led to his kidnapping. But why Milo? Carrie believed that Milo is her biological son.

How does All Her Fault end?

The show’s ending reveals that Carrie, Marissa and Peter were all involved in a car accident that happened years earlier, which supposedly killed Carrie’s newborn son.

Marissa, who was unconscious after the accident, thought that the other woman involved in the accident had later died by suicide.

The truth is revealed when Carrie enters the Irvine house during a heated fight between Peter, his siblings and Marissa’s colleague and friend Colin (Jay Ellis) and explains that she is Milo’s biological mother. Carrie accidentally shoots and kills Colin. In response, Peter shoots and kills Carrie before she can reveal the truth that Marissa’s baby was the one that died in the car accident, not Carrie’s.

Before the police arrive, Peter admits to Marissa that he switched the newborn babies after the car accident. All this time, Marissa and Peter were raising Carrie’s son without Marissa’s knowledge.

Marissa learns about all of Peter’s actions, including that he murdered Rob, Carrie’s dad, who had tried to demand ransom in exchange for Milo. Through a flashback, we learn that Peter brought the money to a hotel room where Rob was waiting, but shot and killed him before the exchange. Peter then took Milo, who was hiding in the bathroom, and placed him in a car trunk where he knew the police would discover the child.

Marissa “accidentally” kills Peter, who has a deadly soy allergy, after she knowingly eats soy and kisses her husband. She had swapped the EpiPen in Peter’s jacket for an expired one and had removed the car’s emergency kit. We learn that Detective Alcaras knew of Peter’s crimes. He also knows the truth about Peter’s death and refuses to investigate it.

The final scene ends with the playdate that was supposed to happen in the first place, with Marissa and Jenny watching their sons, Jacob and Milo, playing together.