Nicholas Noodle has moved to a huge old house. It's not a mansion, it is more like a palace! Nicholas wants very much to explore, but his father has limited the family to a few rooms, and keeps the rest of the house locked up tight. But on the rainy, very boring morning after his 10th birthday, Nicholas finds a little blue door in the corner of his father's study. He goes through into the house and finds himself in a world populated by strange people and even stranger creatures.