Lindsay and Carl Ryder were good at flipping houses. Buy ugly, renovate smart, sell beautiful. They'd done it nine times. The Victorian on Collier Road was number ten. Listed forty percent below market. Four owners in twenty years, none lasting longer than eighteen months.

The previous owner had built strange walls inside the house. Not load-bearing. Not structural. Just walls where walls shouldn't be, sealing off spaces for no apparent reason.

Carl broke through the first one on day three. He found something behind it. He didn't tell Lindsay what.

That was the first secret. Not the last.

The house works slowly. A too-attractive substitute inspector who lingers near Lindsay. A woman's voice whispering to Carl in the basement. Browser histories that neither of them created. A photograph on Lindsay's phone of Carl with a woman she's never seen.

Every crack in their marriage, every silence that lasted too long, every argument they resolved by scheduling instead of talking, the house finds it, widens it, fills it with poison.

By month three, they communicate by text message from different floors of the same house. Both of them are armed. Both of them are certain the other is planning something terrible.

The previous owner didn't build those walls to hide something.

He built them to contain it.