All Her Fault

All Her Fault (2021) by Andrea Mara is a domestic psychological thriller. When wealthy Marissa Irvine goes to pick up her four-year-old son, Milo, from a playdate at her new friend Jenny’s house in suburban Dublin, a stranger answers the door. She does not know Milo, Marissa, or Jenny. Milo has been kidnapped by Jenny’s nanny, Carrie. Marissa and the authorities race to find Milo and to discover why Carrie kidnapped him. The novel deals with themes of The Unrealistic Expectations of Mothers in a Patriarchal Society, The Tension Between Public Personas and Private Realities, and The Impacts of Class on Relationships.

All Her Fault was adapted in 2025 into a Golden Globe-nominated Peacock miniseries starring Sarah Snook as Marissa Irvine. All Her Fault is Andrea Mara’s debut novel.

This guide uses the 2021 Transworld Publishers paperback edition.

Content Warning: The source material and guide feature depictions of anti-immigrant discrimination, child endangerment, child death, graphic violence, and death. The book briefly mentions death by suicide and child abuse.

Plot Summary

All Her Fault is written in shifting third-person limited perspectives with a main timeline that includes periodic flashbacks. For cohesion, this summary is written in chronological order.

Four years before the timeline of the novel, financial manager Peter Irvine and his wife, Marissa, get into a car crash with another car driven by a woman named Carrie. Both cars have infant sons in the backseat. One of the sons dies in the crash. Both Marissa and Carrie suffer serious injuries. After she recovers, Peter pays Carrie to stay away from Dublin, where Peter and Marissa live.

Four years later, Marissa and Peter’s son Milo is four years old. He is bright and has a rare condition called synesthesia, which causes the intermingling of words, numbers, and colors. He attends the exclusive Kerryglen National School. At a school fundraiser, Marissa meets Jenny Kennedy, the mother of another student at the school, Jacob. Marissa and Jenny agree to arrange a playdate for their sons. Jenny’s nanny, Carrie, befriends Marissa’s nanny, Ana, and begins to build a relationship with Milo. Two months after Marissa and Jenny meet, Carrie sets up the playdate for Milo with Jacob over text message.

On the afternoon of the playdate, Marissa arrives at what she believes is Jenny’s house to pick up Milo. She finds only an elderly woman named Esther who does not know Jenny, Milo, or Jacob. Marissa is shaken. She calls the police. They learn that Jenny is on a work trip in Paris and had not arranged the playdate. The police question Ana, Milo’s nanny, but she was off work that day and did not pick Milo up from school. A teacher at the school reports that Carrie, Jacob’s nanny, picked Milo up. They realize Carrie kidnapped Milo.

When she returns from Paris, the police question Jenny about her nanny, Carrie. Jenny reports Carrie was a quiet, unassuming young woman who took good care of her son, Jacob. Jenny searches Carrie’s room and finds a picture of her boyfriend, a career criminal named Kyle Byrde. Jenny goes to Marissa’s house to offer Marissa support during the stressful time. Marissa’s husband, Brian, who is also Peter’s brother, has made flyers to assist in the search for Milo, and Jenny agrees to distribute the flyers.

When Milo has been missing for three days, the police locate and interview Irene, Carrie’s mother. She tells them that Carrie’s father, Rob Murphy, is a career criminal who left when Carrie was young. Irene has since remarried, and she is estranged from her daughter. The next day, the police find Milo’s raincoat near the sea. They fear he has drowned. Marissa is devastated. That evening, Jenny is watching an American television show when she realizes that Carrie had lifted her life story from the TV show: Carrie was pretending to be someone she was not.

The next day, detectives get a call from a witness who reports having seen a man throw Milo’s raincoat on the ground near the sea. They believe it was done to make the police believe Milo had drowned, but Milo is likely still alive. Jenny and Marissa canvass door-to-door with flyers, looking for witnesses who may have seen Milo and Carrie. An elderly man reports he saw Milo with Carrie. Marissa is overwhelmed with the thought of Milo in captivity and collapses.

The next day, Jenny reads a news story about a man who has been found dead in north Dublin. That afternoon, her neighbor tells her he saw Kyle Byrde visit Carrie at their house when Jenny and her husband were out at work. That evening, Marissa asks Jenny to come to her house. While driving over, Jenny learns the dead man has been identified as Danny Vaughn. At Marissa’s house, Jenny learns that an associate of Kyle Byrde was recently arrested for child trafficking. They worry that is what has happened to Milo. After Jenny leaves, Marissa goes to her office with Peter. She works as a solicitor managing financial estates. She prepares files for audits of two accounts with irregularities for her business partner, Colin Dobson, to attend to. Peter helps her search for the files and finds something that seems to surprise him behind the printer.

The next day, Milo is found by a stranger and brought to the local police station. Marissa is relieved to be reunited with her son. Milo reports that he was taken from Carrie’s house, where he was being held by a man wearing a mask, and left in a car. Over the next days, Milo gives the police enough information about where he was being held for the police to identify the house. One evening, Marissa’s sister-in-law is looking at photos of her old school friends on Facebook when she realizes she can see Colin having a date with Carrie in the background of one of the pictures.

The next day, Marissa intends to confront Colin, but he calls in sick to work. That evening, the police detective informs Marissa that the dead man, Danny Vaughn, is in fact Kyle Byrde, Carrie’s boyfriend. They do not believe Carrie would be capable of killing Kyle in such a gruesome fashion, and they suspect there is another person involved in the kidnapping scheme.

The next day, the police find the house where Carrie had held Milo. They discover her body, as she has been smothered to death. That same day, Peter and Marissa go to Colin’s house to confront him about dating Carrie. He admits he did so, but he claims he did not know the woman he saw was Carrie, as she disguised herself and went by the name “Lena.”

The next day, Marissa goes over the work files. She realizes Colin had stolen over half a million Euros from their clients. The next day, she intends to report him to the police. That evening, however, a detective arrives to tell her that Colin has been found shot to death. It is believed he was intending to give a large sum of money to Rob Murphy when Rob killed him. Before he died, Colin shot Rob. They are both dead.

The next day, the police inform Marissa that they believe Carrie and Rob kidnapped Milo with the intention of taking him out of the country. That evening, while Marissa is tucking Milo into bed, he tells Marissa that the man who took him out of Carrie’s home called him “Milo-Mouse.” This is Peter’s pet name for his son. Marissa is shocked.

Marissa confronts Peter. He confesses to everything. He tells her that in the car crash four years prior, their infant son had died. Before the authorities arrived, he had swapped their young son for Carrie’s. He had then paid Carrie to stay away. When Carrie realized Milo was her son, she confronted Peter. She then got a job as a nanny for a boy in the same class as Milo to get close to him. At Marissa’s office, Peter had discovered the address where Carrie was keeping his son. Instead of informing the police, he had gone to the house, killed Carrie, and put Milo in the car, where he would be found without bringing suspicion on himself. Rob Murphy discovered the murder and blackmailed Peter. Peter then used his knowledge of Colin’s theft to blackmail Colin into bringing the money to the handoff. Peter followed him. After Rob ambushed Colin and killed him, Peter shot and killed Rob, and then put the gun in Colin’s hand. Marissa is shocked. She wants to report this to the police, but she is afraid that if she does so, the authorities will take Milo away. She decides against telling them. She believes that Rob Murphy possibly killed Kyle Byrde when he advocated for returning Milo to the Irvines.

A month later, Marissa and Peter go on vacation to Spain. The news later reports that Peter, who had a severe shellfish allergy, has died while there. Marissa prepared a meal containing shellfish, and Peter died when Marissa could not find his EpiPen.