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Olivia is ten and a half, and she lives a double life: she lives with her mum for a week and her dad for a week. It seems to be even fun! One house is full of people and animals, the other is clean and quiet. When you get bored in one house, it's time to move to another. But here's the rub: the dad and his new wife will soon have a baby, and Olivia will no longer be a "favourite child"! All attention will be focused on the baby, and the house will be in complete chaos. As if on cue, a new girl has appeared in the class, taking Olivia's favourite spot and drawing all the attention. No wonder Olivia is confused and upset, and even starts to do something stupid.
But everything changes on Christmas Eve, when Olivia and the new girl become friends. And Olivia wants to spend the holiday in the hospital, because her newborn sister is there. So both Olivia's families are going to congratulate the baby, because Christmas is a time of real miracles and family comfort.