Today would have been Grandpa's 90th birthday, but he is no longer here. However, Finn remembers the stories he always told him: about a place where the sea and sky meet, where whales and jellyfish, where birds and ships and castles float freely in the air. Finn has the perfect idea for how to celebrate his grandfather's special day: he will set sail and find the magical place that Grandpa talked about so often! And maybe he will even be able to say a proper goodbye to his grandpa along the way.