It’s Christmas, and the Birch family are coming together at their second home in Norfolk. Emma and Andrew’s daughter, Olivia, is back for the first time in years, and while Emma is elated at them all being under one roof, her younger, more frivolous daughter Phoebe is braced for inevitable clashes. But aid worker Olivia is only home because she has nowhere else to go. Having recently returned from Africa, where she’s been treating a life-threatening virus, she has been told that she must stay in quarantine for a week, and so, too should her family. For the next seven days, no one can leave the house, and no one can enter. It doesn’t sound too hard. But a week with your nearest and dearest can feel like an eternity, especially when they’re all harbouring secrets.