William and his brother are desperate to have a tree house in the grand old tree at the bottom of the garden. Their father has to go away, but is determined that the tree house should be built. So every month he sends a parcel home to the boys - a parcel containing things they'll need for the tree house. But will their father be home in time for Christmas - in time to join them in the tree house to eat the chestnuts that are growing there . . .