All About the Real-Life Incident

All Her Fault depicts every parent’s worst nightmare.

Based on Andrea Mara’s 2021 novel of the same name, All Her Fault tells the story of a mother, Marissa Irvine (Sarah Snook), who goes to pick up her son Milo from a playdate, only to find that the person who opens the door is a stranger who has never heard of her child.

As the search for Milo begins, more lies start unraveling amongst the characters, who are portrayed by a star-studded cast including Dakota Fanning, Jake Lacy, Jay Ellis and Abby Elliot.

As tensions grow, Marissa develops an unexpected friendship with Jenny Kaminski (Fanning), despite being “set up to have a tumultuous relationship,” as Fanning told PEOPLE ahead of the series release.

So, is All Her Fault a true story? Here’s everything to know about the real-life event that inspired the series.

Warning: All Her Fault spoilers ahead.

Is All Her Fault based on a true story?

All Her Fault is not based on a true story, but real-life events inspired it.

In a June 2021 video introducing her novel, Mara — who is also an associate producer on the series — shared that the plot is based on an experience that occurred in April 2015, when she went to collect her daughter from a playdate, only to find herself standing outside an unoccupied 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,” the author said. “It all ended very quickly, much more quickly than it does for Marissa in the book.”

Mara revealed more about the incident in a July 2021 essay for The Irish Independent, writing that she began theorizing about an “elaborate kidnap plan” after nobody answered the door for a few tries.

Though she reconnected with her daughter nearly five minutes later, the moment made Mara think about “how much trust we place in other people when it comes to our kids; when we send them off to school and crèche and 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 in All Her Fault?

After Milo goes missing, Marissa and her husband Peter (Lacy) launch a frantic search for their son. Once detectives get involved, Jenny’s nanny, Carrie Finch (Sophia Lillis), becomes the prime suspect. Milo is eventually returned, but Carrie — whose real name is Josephine Murphy — remains at large.

The penultimate episode flashes back six years, showing how losing her newborn at 16 drove Carrie to mental instability and fueled her obsession with Milo, ultimately leading to his kidnapping. But, viewers learn that her obsession with Milo isn’t random: Carrie actually believes he is her son.

By the final episode, Carrie enters the Irvine family home — in the middle of a blowout fight between Peter, his siblings (Abby Elliot and Daniel Monks) and Marissa’s longtime friend and colleague Colin Dobbs (Ellis) — and explains that she believes Milo is her son.

The series reveals that Carrie, Marissa, and Peter were involved in a devastating car accident years earlier that supposedly killed Carrie’s newborn. Marissa, who was unconscious after the accident, thought that the mom, then known as Josephine, had died by suicide after the wreck. But in reality, it was Marissa’s baby, not Carrie’s, who died that night.

After accidentally shooting and killing Colin in a struggle for the gun she brought, Carrie insists she is only here to warn Marissa about Peter. Peter shoots Carrie before she has a chance to tell Marissa the whole story, but admits the truth to his wife just before the police arrive: he switched the newborn babies after the wreck.

By the end, Marissa learns the truth of all of Peter’s actions — including that he murdered Carrie’s dad, who had tried to demand a ransom in exchange for Milo — and “accidentally” kills Peter by kissing him and sending him into a severe allergic reaction from something she ate.

With Peter’s death ruled an accident and the case closed, the series ends with Milo enjoying a playdate with Jenny’s son after all.

What has author Andrea Mara said about the All Her Fault adaptation?

During a June 2024 conversation with The Irish Times, Mara discussed how many of her thriller novels are inspired by real-life stories, though she acknowledged that all of them “ended pretty quickly with reasonable explanations.”

But, to lean into the fictional versions, the author said she focuses on the “what if.”

“What if my child was kidnapped on a playdate, what if my child disappeared on the Tube, what if there really was someone living in the attic?” she said, referencing some of the story lines of her other novels.

In the interview, she also talked about living with Synaesthesia — the neurological condition where sensory crossovers occur — that connects Milo and Carrie in All Her Fault.

In early November, Mara shared photos on Instagram after attending the All Her Fault premiere, and opened up more about the true elements of the show.

“The book is about a missing child, yes, but it’s also hugely about female friendship, and this has been carried through to the TV show,” she captioned the carousel. “I know a lot about female friendship and women supporting women because of the wonderful people I’m lucky to know in real life. So even if the kidnap element of the real life inspiration is fictional, the friendship element is absolutely true.”

Where can I watch All Her Fault?

All eight episodes of All Her Fault are available to stream on Peacock.