On her forty-fifth birthday, celebrated in her local pub, renowned podcaster Alix Summer stumbles upon a woman named Josie Fair, who is also marking her forty-fifth year. They realize they share the same birthdate, making them birthday twins.

A subsequent encounter outside Alix’s children’s school further intertwines their lives. Josie, having listened to Alix’s podcasts, considers her an intriguing subject for a series and confides in Alix that she stands on the brink of significant life changes.

Josie’s existence seems tangled and mysterious, and while Alix is somewhat unnerved by her, she is drawn to continue producing the podcast. Gradually, she comes to understand that Josie is concealing some ominously dark truths. Almost without realizing it, Alix finds that Josie has insidiously woven herself into her life and home.

Then, as suddenly as she appeared, Josie vanishes, leaving behind a chilling and horrifying legacy. Alix finds herself thrust into the role of the subject of her own true crime podcast, her life and the lives of her family now under a deadly menace.

The questions loom large: Who exactly is Josie Fair? And what unspeakable acts has she committed?