The Island (Prince Caspian, Chapter One)
Once, there were four children whose names were Peter, Susan, Edmund and Lucy, and it has been told in another book called “The Lion, the Witch and the Wardrobe” how they had a remarkable adventure. They had opened the door of a magic wardrobe and found themselves in a world quite different from ours, and in that different world, they had become Kings and Queens in a country called Narnia. While they were in Narnia they seemed to reign for years and years; but when they came back through the door and found themselves in England again, it all seemed to have taken no time at all. At any rate, no one noticed that they had ever been away, and they never told anyone except one very wise grown-up.