Johan and his father have lived alone on an old ship for as long as Johan can remember. They have a good life together, but something is missing. One day, when Johan's father has gone ashore to get supplies, Johan is alone on the ship and receives a mysterious call over the radio. His mother is in the Kingdom of the Feather King.
Johan travels there to bring her back, but discovers that the kingdom is about to sink into the ocean. The Feather King needs Johan's help.