The roads around Dingle are whisper-quiet in the small hours of a rainy night, empty of the tourists who throng the town by day. As she and her assistant, Patrick, drive home after an already traumatic day, Dimpna Wilde isn't expecting to see anyone, let alone her employee, Niamh, standing in the road, dressed in a nightgown and soaked to the skin.

Dazed and distraught, Niamh passes out after muttering incoherently, and at her apartment, Dimpna and Patrick make a grisly discovery. There's a dead woman in Niamh's bed, shot in the head, a hunting rifle beside her. When Niamh comes to, she has no memory of the day's events, and no idea of the woman's identity. All she can tell Detective Inspector Cormac O'Brien with certainty is that for weeks, she's felt like she was being watched.

Suspicion falls on Niamh's new boyfriend, Mark Gallagher, who her friends have not yet met. But as Dimpna and Cormac try to track him down, they realize there's no evidence Mark Gallagher ever even existed. All of Niamh's texts and photos of him are missing or deleted, and he has no social media presence. What lingers is a nagging unease, especially when they learn of another, similar murder years ago--another woman found shot to death in her bed, a woman who had complained of being stalked, just like Niamh.

As Dimpna delves deeper into a twisting case, she feels someone watching her too, targeting her business, her animals, her family--even her sanity, willing to do anything to stop her from disclosing a terrifying truth . . .