Karen and Tom Krupp are happy. They have a lovely home in upstate New York, they're practically newlyweds, and they have no kids to interrupt their comfortable life together. But one day, Tom returns home to find Karen has vanished--her car's gone and it seems she left in a rush. She even left her purse, complete with phone and ID, behind.
Then a knock: the police are there to take Tom to the hospital where his wife has been admitted. She had a car accident, and lost control as she sped through the worst part of town. The accident has left Karen with a concussion and a few scrapes. She's okay, except for not remembering where she was going or what she was doing, which the cops think is highly convenient--they suspect she was up to no good.
Karen returns home with Tom, determined to move on. But something's not quite right. Someone's been in her house. And the police won't stop interrogating her.
In this house, everyone's a stranger. Everyone has something they'd rather keep hidden. Something they might even kill to keep quiet.