All Her Fault season 1 ending explained: Why did Carrie kidnap Milo?

All Her Fault season 1, created and show-run by Megan Gallagher, adapts Andrea Mara’s bestselling novel into a taut thriller television series. The story follows Marissa Irvine, whose son Milo disappears after a playdate, triggering a nightmare of suspicion, secrets, and social scrutiny. The series comprises eight episodes that dropped simultaneously on Thursday, November 6, 2025, on Peacock.

Disclaimer: The following article has spoilers for All Her Fault season 1. Reader’s discretion is advised. 

Carrie Finch, who works as a nanny at Marissa’s friend’s place, turns out to be the one responsible for kidnapping Milo. In the penultimate episode of All Her Fault, it is revealed that her real name is Josephine Murphy, and she has been living in trauma since losing her child in a road accident at the age of 16. She confesses to Marissa in the finale that her attachment to Milo stems from her conviction that he is actually her biological son.

She thus organized Milo’s kidnapping with assistance from her criminal boyfriend, Kyle Smit, and her gambler father, Rob Murphy. Even after Milo has been reunited with his family, Carrie comes blazing in with a gun, demanding to be reunited with the child. 

What happened to Carrie in All Her Fault?

As Carrie keeps Marissa, her husband Peter, and their friends at gunpoint, she is briefly distracted when Milo’s voice calls out for his mother from the nanny cam. As she insists that she will never hurt Milo, Marissa’s best friend and business partner, Colin, tries to take the opportunity to disarm Carrie. In the tussle that follows, Colin gets shot in the stomach by accident. 

A horrified Carrie begs for someone to call an ambulance, and Peter sends a distraught Lia outside to wait for help. Brian goes to comfort Milo as Peter quietly confirms that Colin has died. Marissa then demands that Carrie come clean about everything, following which the latter reveals her true identity and tells Marissa to protect Milo from Peter. 

She reaches for her phone to reveal a long-buried secret with proof, but Peter lunges at her and ends up killing her with her own gun. While he tries to play it off as self-defense, Marissa refuses to believe him. In the end, Peter comes clean, telling her that when he and Marissa had gotten into a car accident with their infant son, the baby did not make it. However, in the other car involved in the crash was Josephine and her baby, still alive but unconscious. 

With Peter being the only person at the scene who had not lost his senses, he used the opportunity to swap the babies. Milo has indeed been Carrie's biological son all along. When the police arrive, Marissa does not give up her husband, but stands by his story of killing Carrie in self-defense. 

How does Peter die in All Her Fault?

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Marissa is unable to forgive her husband for his actions, and later discovers from Carrie’s phone that he also killed her father when he tried to extort him for money. Soon, Marissa feels increasingly trapped, fearing she can neither divorce Peter nor give him up to the police without severe consequences. 

She turns to her friend Jenny, who reassures her that Milo truly belongs with her. Ultimately, Marissa came up with a plan to get rid of her husband. At Colin’s wake, which she has helped organize, Marissa deliberately consumes soy, knowing Peter’s severe allergy. She then goes on to passionately kiss him, triggering a fatal reaction. To have her bases covered, she also sabotaged his EpiPen by replacing it with an expired one and leaving the real one in the car. 

As the others wait helplessly for the ambulance, Peter dies before help arrives. Later, Detective Alcaras uncovers the truth about Milo and figures out what might have gone down within the family. However, he does not hold Marissa responsible for the family and considers the case closed. 

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