Amanda and Clay head to a remote corner of Long Island expecting a holiday: a quiet reprieve from life in New York City, quality time with their teenage son and daughter and a taste of the good life in the luxurious home they've rented for the week. But with a late-night knock on the door, the spell is broken. Ruth and G. H., an older couple who claim to own the home, have arrived there in a panic. These strangers say that a sudden power outage has swept the city, and - with nowhere else to turn - they have come to the country in search of shelter.

But with the TV and internet down, and no phone service, the facts are unknowable. Should Amanda and Clay trust this couple - and vice versa? What has happened back in New York? Is the holiday home, isolated from civilisation, a truly safe place for their families? And are they safe from one another?