When Emma, a ghostwriter, moves to a new town to start afresh with her ailing mother, she unexpectedly becomes entangled in a web of mystery surrounding her sister's murder. A chance encounter with Nick, a writer renting space in her new home, leads Emma to a bizarre project: a fiction novel detailing the diary of a serial killer. As Emma delves deeper into the project, she begins to question the line between fiction and reality, all while confronting her own past and forming unexpected alliances.