It's December 23rd and Clara Dunphy is running around Oxford Street like a blue-arsed fly trying to buy presents. She wants to make Christmas perfect: it's a lifelong ambition. And a challenging one at the best of times, even without taking her sixteen guests - sorry, "loved ones" - and their varying degrees of social dysfunction into account. Meanwhile, something weird has happened to her marriage, and the ho, ho, ho is thin on the ground.Why does Christmas have such an emotional hold over us? ...