All Her Fault ending explained: Who was Carrie and why did she take Milo?

*Warning: This article contains full spoilers for the final episode of All Her Fault.*

Across eight episodes, All Her Fault takes on quite the quick-paced journey from Milo's (Duke McCloud) initial disappearance right through to when it becomes hauntingly apparent just who took him.

The mysterious nanny of Jenny's (Dakota Fanning), Carrie Finch (Sophia Lillis), appeared to have a fascination with Milo and took him after befriending Marissa (Sarah Snook) and Peter's (Jake Lacy) nanny, Ana (Kartiah Vergara).

But why did she take him and why was she not asking for any ransom money? Thankfully, those questions weren't at the top of priorities in the penultimate episode as Marissa and Peter were reunited with Milo at long last. However, the drama didn't stop there as in the middle of the evening, Carrie herself appeared in their home wielding a gun at them, asking for her son.

But what happened and why did Carrie take Milo in the first place? Read on to find out more about what unfolded in the final episode of All Her Fault.

All Her Fault ending explained: Who was Carrie and why did she take Milo?

As Carrie continues to point the gun at everyone, she's momentarily distracted by Milo calling for his mother on the nanny cam that they have in the living room. She admits that she'd never do anything to hurt Milo but Colin (Jay Ellis) takes that as his chance to try and play hero, getting into a tussle with Carrie who shoots him in the stomach.

Carrie says she didn't mean to do it and urges someone to call an ambulance, with Peter urging an emotional Lia (Abby Elliott) to go outside and wait for help there. Brian (Daniel Monks) goes to soothe Milo but once he's left the room, Peter silently confirms that Colin is in fact dead.

Marissa then asks Carrie the question we've all been wanting to know the answer to – who is she and why did she take Milo?

Carrie explains that her real name is Josephine Murphy and immediately, Marissa knows who she is but is shocked by the admission, stating that Josephine must be dead. Carrie admits that she wishes she was but then goes on to say that she feels as though she "lost" six years ago. She urges Marissa to promise her, mother to mother, that she'll protect Milo from Peter.

"You don't know what he's capable of," Carrie tells Marissa. Carrie then tries explaining that one night years ago, before the ambulances came, Peter did something that he's clearly never told Marissa about. As Carrie tries to retrieve her phone out of her back pocket to get Marissa to listen to a recording, Peter lunges at Carrie.

He manages to turn the gun on a scared Carrie and shoots her dead. Peter immediately tries to reframe the story, telling Marissa that the gun just went off but Marissa knows he killed Carrie intentionally because he didn't want Carrie revealing something.

Marissa doesn't back down and orders Peter to tell her the truth about what happened on that fateful night. On their way home from the hospital with newborn Milo, they'd gotten into a car accident with an oncoming vehicle. Peter, the only one conscious on impact, turns around to find Milo dead and Marissa appearing to be the same. Of course, we know she survived and get a flashback to her shoulder scar, which is now explained by the tragic car collision.

In the present, Peter tells Marissa that actually, their son did die in the accident. But flashing back to the night in question, after he called 911 for help, Peter hears a baby crying. He goes into the other crashed car and retrieves a newborn baby boy, cradling him as he hears sirens in the distance. He tells Marissa that he didn't plan it but reveals that he switched the babies, thinking that Carrie was dead in her car.

He says that because she was alone in her car, it seemed as though she couldn't give Milo the life that they had given him and she didn't seem fit to be his mother. He explains that he saved them all from a lifetime of grief and tells Marissa that she can't tell anyone about this because Milo may be taken away.

When the police arrive they confirm that the other two bodies they've found in their investigations have been that of Carrie's boyfriend and of her father. Peter explains the confusion he had about Carrie/Josephine and not recognising her mugshot initially. But Detective Alcaras (Michael Peña) suspects something is amiss, especially after Carrie allowed Lia to call an ambulance and for Brian to tend to Milo.

Having hidden Carrie's phone to listen to for herself, Marissa listens to the recording. It reveals that Peter went to go and visit Carrie's father at a motel, who told Peter that Carrie suspected that something was wrong with the car accident and that Milo was in fact hers. Peter has come with a bag of ransom money for Carrie's father but hits him over the head with a lamp, telling his dead body that he saved Milo and that he's his.

Peter then explains that he was actually the one to retrieve Milo but covered his eyes and left him at the police station so that it wouldn't implicate him being at the motel.

Speaking exclusively to RadioTimes.com about his character's actions, Jake Lacy said: "The fun thing with Peter is that, he has a very clear sense of why he's done this and has no regrets - and that's crazy. There’s no part of him that's like, ‘I see where you're coming from.’ He's like, ‘You're wrong, I did this because I love you and you're wrong’. It's just narcissism.

"My reasoning is that, in shock, in the chaos of the moment, in believing that Milo's biological mother is deceased, in the shock of his own newborn now dead, he believes that he can save his wife from the grief of losing a son – that he has kept a family intact. At least that's what he's told himself. If you can lean on that as an actor, then then you're doing this really selfless thing, even though everyone else in the world is like, ‘You don't get to play God’. That’s not how this works, Peter."

What happens to Peter?

As life starts to return to normal, it becomes clear that Marissa doesn't trust Peter generally and with Milo, with Peter clearly showing some control issues. She texts Jenny telling her that she needs to see her. When she goes to visit Jenny, she tells her the whole truth about what's happened and what Peter has done. She tells Jenny that she's scared of Peter and what could happen if she chooses to get a divorce.

When he takes his son to the doctor, Detective Alcaras then learns of synaesthesia, a neurological condition that can see those affected experience a joining of the senses. It triggers a memory of Milo and he then calls up one of Carrie's former teachers who confirms his suspicions – that it seemed like she had it also.

The day of Colin's funeral, Peter and Brian share some tense words as Brian says he's going to be moving and getting a new job. He also has a tense confrontation with Lia and later on, is found in Colin's basement cellar by Marissa. The pair share a passionate kiss but immediately after, Peter starts choking, starting to feel the onset of an allergic reaction.

He goes to retrieve his EpiPen from his jacket and uses it to find that actually, it's expired. Marissa is in charge of Peter's medication and states that she wouldn't have gotten them mixed up. Marissa tells Lia to call 911 and get the emergency kit from the car but when she returns, she tells them that it's not there. The ambulance is 8 minutes away and nobody in the growing crowd has an EpiPen.

As he continues to choke, Peter tells Marissa that she always has the emergency kit and that's when she confirms it – that this is part of her plan to kill Peter. We get a flashback to that morning where she purposely removes the emergency kit from the car and retrieves an expired pen from the rubbish instead, thereby sealing Peter's fate. Detective Alcaras then gets a call confirming that Peter is indeed dead.

On his character dying at the end of the series, Lacy told RadioTimes.com of his reaction: "Well, I was bummed because I like Peter. I always have more affinity for these unpalatable people than maybe an audience does or other characters do. But also, [it] feels inevitable.

"You're like, ‘There's no way he continues on in the world.’ This has to end in one place or another and is really fulfilling, as a story is really fulfilling. Plus, as an actor, you get to have a death scene and that's fun. It’s fun, that's why I love doing this since I was a kid, just play pretend through all these wild things, just play pretend.”

What happens to Marissa?

The following day, Lia is brought in for questioning by the police where it's revealed that Marissa must've consumed something with soy in, which is what Peter was severely allergic to. Lia went to lengths to make sure everything was correctly labelled and the police ask her if Marissa checked the food labels or simply forgot to do so.

We see that in fact, Marissa had read the labels and Lia had seen her doing so. But when she's pressed for an answer by the police, Lia remembers the awful way in which Peter spoke to her at the wake and lies for Marissa.

Some time has passed when we next see Marissa at home with Milo, where she's packing things up to move. She's visited by Detective Alcaras, who mentions the synaesthesia he's found out about that both Milo and Carrie had. He tells Marissa that he knows she was unconscious and wasn't privy to any decisions that Peter made, also telling Marissa that he thinks Peter killed Carrie's father and put Milo in the trunk of the car. He also acknowledges that Marissa would've only found out about all of this when Carrie appeared at her door and she would've had to make some difficult decisions of her own.

Although he has cracked the case, he tells Marissa that it's actually officially closed now. Even though it shouldn't sit right with him, he admits he feels fine and leaves.

We then see Marissa and Milo go bounding down the road to see Jenny and her son, enjoying an evening together smiling and sipping wine.

All Her Fault lands on Sky and NOW as a boxset in the UK on Friday 7th November.

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