Amelia the mouse lives in the roof of a terraced house outside the big city and is pursued by Oscar the cat whenever she leaves her home in the roof to search for food. It is the week before Christmas and Amelia has realised she has not posted her Christmas letter to Santa and leaves her home in the roof to travel into the city where Santa has a grotto in one of the big department stores. On her way to post her letter Amelia encounters many acts of kindness and hears of something called the spirit of Christmas . In her quest to understand what the spirt of Christmas is she learns the true value and meaning of Christmas and the Christmas message.