If you think Platform 9 and 3/4 is the only unusual one at King's Cross station in London, think again. In this book, originally published years before Harry Potter arrived, there is a doorway under Platform 13 that leads to a magical island world filled with mermaids, ogres and mistmakers. But when the island's Prince was a baby, he was kidnapped and taken to London where he's being raised as a human boy. Now the King and Queen send a hag, a wizard, an ogre and a fey to the big city to retrieve their son and bring him home. Will the rescuers succeed? Will they be unnoticed by humans?