Just because All Her Fault is based on a novel by Andrea Mara doesn't mean the TV adaptation didn't go through some book-to-screen changes. The Peacock series, which premiered Thursday, November 6, follows a mother named Marissa (Sarah Snook) whose son, Milo, disappears from his first playdate. The search for Marissa's child uncovers secrets about those closest to her, with everyone becoming a suspect in the kidnapping. While All Her Fault has largely stuck to its source material, the biggest differences came from expanding on characters including Abby Elliott's Lia and Daniel Monks' Brian.