The other Mrs.

Sadie and Will Foust leave Chicago for a small island off the coast of Maine, moving into the house Will inherited from his sister after her sudden death. His troubled teenage niece, Imogen, comes to live with them. The neglected old house, with its unsettling attic, feels wrong from the first night.

Then a neighbor, Morgan Baines, is found murdered in her own home. The island turns its suspicion on the family that just arrived. Sadie starts asking questions about Morgan, and each answer exposes something she would rather not know about her husband, her niece, and the marriage she thought she understood.

The novel splits its telling across shifting narrators and timelines, layering the investigation with glimpses of what came before it. As Sadie gets closer to the truth about Morgan's death, she has to decide how much of her own family's past can surface with it.

It is a dark, fast-moving psychological thriller built around an unreliable narrator, working toward a reveal that changes how everything before it reads. The danger, by the end, is as much inside the marriage as outside it.