Everyone's welcome. But not everyone leaves…

Nick and Amber Miller are splitting up and selling their Devon family home. But despite the desirable location, the house isn't moving. Not a single viewing so far.

When their estate agent suggests an open house event, Amber agrees, even as she worries about their gossiping neighbours attending and snooping around their home.

But Amber has more to worry about than nosy neighbours. Because thirteen people enter her house that afternoon, and only twelve leave.

Someone doesn't want the house to sell, and is willing to do anything to stop it…