All Her Fault reveals shocking twist ending with Sarah Snook’s brutal murder on Peacock

All Her Fault delivers a devastating ending that rewrites everything. Sarah Snook’s character uncovers a shocking truth about her husband. The Peacock thriller reveals dark secrets buried for six years. By the finale, November 11, 2025, multiple characters fall victim to murder.

What Happened in the Finale?

When Carrie Finch (Sophia Lillis) appears at the Irvine home with a gun, everything falls apart. She reveals her true identity: Josephine Murphy. Six years earlier, Josephine and Marissa were in a devastating car accident. Josephine’s newborn died in the crash. Or so Marissa believed.

“I never wanted to hurt anyone. I wanted to warn you about him. I wanted to keep Milo safe.”

Peter (Jake Lacy) killed Josephine’s father Rob at the motel. When Josephine threatens Marissa with the gun, Peter shoots her dead. Then he confesses his crime to Marissa: he switched the babies.

The Shocking Baby Swap Revelation

During the car accident six years ago, Marissa was unconscious. She heard an infant crying from Josephine’s wrecked car. Peter made a choice in seconds. He grabbed Josephine’s living baby and left his dead son. This wasn’t an accident. Peter moved the babies deliberately.

Peter thought Josephine was dead at the scene. He believed the living infant needed a family. But his justifications kept shifting throughout the episode. He convinced Marissa to stay silent about all of this. The boy she raised for six years wasn’t biologically theirs. Milo belonged to Josephine.

Detective Alcaras (Michael Peña) discovers the truth about babyswap. Both Josephine and Milo have synesthesia, a hereditary condition. The detective realizes Milo is genuinely Josephine’s biological son. His unusual color choices in drawings match his mother’s condition.

How Marissa Takes Her Revenge

Weeks after Josephine’s murder, Marissa plots vengeance. She attends Colin’s funeral with her family. During the reception, she plans something calculated. Peter is allergic to soy and requires constant vigilance.

Event	What Happens
Kiss at Funeral	Marissa deliberately eats soy before kissing Peter
Allergic Reaction	Peter’s throat swells rapidly from soy exposure
Missing EpiPen	Expired pen in jacket; emergency kit removed from car
Eight Minute Wait	Ambulance arrives too late; Peter dies before help reaches him

Marissa orchestrated this perfectly over weeks. She removed the working EpiPen days before the funeral. She replaced it with an expired one. She meticulously planned every detail of his death. Peter dies realizing his wife poisoned him deliberately.

Key Characters and Their Fates

• Sarah Snook as Marissa Irvine: Gets away with murder; raises Milo.
• Jake Lacy as Peter Irvine: Dies from soy-induced anaphylaxis at funeral.
• Sophia Lillis as Carrie (Josephine): Shot by Peter before revealing truth.
• Dakota Fanning as Jenny Kaminski: Becomes Marissa’s loyal confidante.
• Michael Peña as Detective Alcaras: Covers for Marissa by ignoring evidence.

What Happens to Milo?

Milo survives the entire ordeal unharmed physically. Peter abandoned him at the police station to cover his crime. The boy was returned to the family after secretly hiding in a motel. Marissa now raises him as her son, knowing the truth.

The series ends with Marissa and Jenny watching their sons play. They sip wine on a porch in peaceful silence. The boys blow bubbles while the mothers smile knowingly. Milo is finally safe with Marissa.

Why Detective Alcaras Lets Her Go

Alcaras visits Marissa at home after Peter’s death. He reveals he knows exactly what happened. She killed her husband to protect Milo from danger. He tells her he feels “fine” not investigating further.

“I know what Peter did. I know what you did. I’m willing to overlook it because Milo needs a parent.”

Justice and the law aren’t always the same thing. Alcaras recognizes that Peter was a monster who deserved punishment. He chooses moral justice over legal justice. Marissa remains free to raise Milo without legal consequences.

What Comes After the Ending?

The series concludes with Marissa and Milo at Jenny’s home for a playdate. Everything appears normal on the surface. But the weight of secrets hangs heavy in the air. Marissa saved her son by destroying everything else.

She made impossible choices to protect the child she raised. She poisoned her husband to keep Milo safe from further harm. The series never judges her actions—it simply presents them. Marissa chose love over law, protection over punishment.

Streaming all eight episodes on Peacock right now reveals every twist. The finale proves that truth destroys families. But sometimes love requires crossing moral lines. All Her Fault transforms a missing child thriller into a study of motherhood.

Sources

• TIME – Breaking Down the Devastating Ending of All Her Fault
• People – All Her Fault Ending Explained: What Happened to Carrie and Milo
• Peacock – All Her Fault Official Streaming Page