Peacock’s ‘All Her Fault’ Series Diverges from Andrea Mara’s Novel

Peacock’s new mystery series, All Her Fault, which premiered in November 2025, presents a gripping narrative that diverges significantly from its source material, a novel by Andrea Mara. The show follows Marissa, portrayed by Sarah Snook, as she navigates the harrowing disappearance of her son, Milo, from his first playdate. As the investigation unfolds, hidden truths about Marissa’s close relationships surface, transforming everyone into a potential suspect.

The adaptation has sparked interest not only for its suspenseful storyline but also for the notable alterations made in character development and plot. Stars Abby Elliott and Daniel Monks, who portray key roles in the series, discussed these changes in an exclusive interview with Us Weekly. Monks emphasized that his character, Brian, felt “unrecognizable” compared to how Mara depicted him, leading him to focus primarily on the television scripts rather than the book.

Character Transformations and Storyline Changes

Both Elliott and Monks experienced significant shifts in their characters. Elliott, who plays Lia, noted that she was advised not to read the book initially to avoid preconceived notions. Lia’s character, originally less involved in the storyline due to her being in New York while the Irvines resided in Dublin, underwent an evolution for the show. In the series, she grapples with a past substance abuse issue and is seen in a clandestine relationship with Marissa’s business partner, Colin, played by Jay Ellis, prior to his shocking death.

While Brian’s backstory remains intact from the book, the show introduces a new layer by revealing that he became disabled due to an accident during their childhood, adding depth to his character and creating additional intrigue.

The friendship between Marissa and Jenny, played by Dakota Fanning, also takes a different direction. In the series, Marissa confides in Jenny about her intentions regarding Peter, which did not occur in the original narrative.

Significant Plot Changes and Character Arcs

The adaptation also alters Jenny’s personal life. In the book, her marital issues stem from a difficult relationship with her mother-in-law, while the show opts for a more permanent split, presenting a stark contrast in her storyline.

One of the most striking differences involves the portrayal of significant deaths within the narrative. The circumstances surrounding these deaths differ dramatically; for instance, the show depicts Rob murdering Kyle in a different context compared to the book. Additionally, Peter’s method of killing Carrie shifts from a shooting in the book to smothering her with a pillow in the show, showcasing a darker twist.

The background of Carrie, played by Sophia Lillis, is also less developed in the series. While the book delves into her mother’s manipulative behavior regarding Carrie’s legal troubles, the show opts for brevity in this aspect.

Moreover, Detective Alcaras, portrayed by Michael Peña, receives a more substantial role in the limited series. His personal connection to the case, which is only briefly mentioned in the book, is expanded upon, providing viewers with a deeper understanding of his motivations.

While All Her Fault captures the essence of the original story, it distinctly reimagines characters and events, creating a unique viewing experience. The series highlights the complexities of relationships and the dark secrets that can emerge in times of crisis, leaving audiences eager for the unfolding mystery.