Hidden beneath Platform 13 at King's Cross Station lies a magical doorway that opens only once every nine years, leading to a fantastical island inhabited by ogres, hags, mermaids, and mistmakers. Nine years ago, the island's baby prince was stolen and lost in London. Now, a peculiar rescue party—comprising a wizard, an ogre, a hag, and a young human girl—must find him and bring him back. However, the prince has grown into a spoiled rich boy who doesn't believe in magic and refuses to return home. Can the rescue team convince him before the doorway closes forever?