Claire and Matt are divorced but decide what's best for their daughter Scarlett is to have a 'normal' family Christmas. They can't agree on whose idea it was, or who said they should bring their new partners. But someone did - and it's too late to pull the plug. Claire brings her new boyfriend Patrick, a seemingly eligible Iron-Man-in-Waiting. Matt brings the new love of his life Alex, funny, smart, and extremely patient. Scarlett, their daughter, brings her imaginary friend Posey. He's a rabbit. Together the five (or six?) of them grit their teeth over Organized Fun activities, drinking a little too much after bed-time, oversharing classified secrets about their pasts and, before you know it, their holiday is a powder keg that ends - where this story starts - with a tearful, frightened, call to the police...