She thought her ex-husband was giving her a second chance. He was giving her a warning.

When Monica Reyes signs the papers on the house she used to share with her ex-husband, she tells herself it's a peaceful new start for their daughter. A fresh beginning. A house full of good memories instead of bad ones.

But the moment she moves back in, she finds a room in the basement that was never there before. Locked. Soundproofed. Empty except for a single chair, bolted to the floor.

Her ex-husband says it's nothing. A mistake. A leftover from renovations.

He's lying.

As Monica digs deeper, she learns her house has a history far darker than her own marriage — a missing girl, a family that never spoke of what happened, and a man who never really let go of the home he lost. Someone has been living in the walls. Watching. Waiting. And the closer Monica gets to the truth, the more she realizes the biggest danger isn't a stranger at all.

It might be the man she trusted the most.