Joining an expedition to chart the southern seas, twelve-year-old mapmaker's assistant Sai, posing as a well-bred young lady with a glittering future, realizes she's not the only one on board harboring secrets when she discovers the ship's true destination.

Quinn, Ash, Zain and the crew of the Libertas are racing against the clock to get back to Verdania before the King's deadline. Will they make it in time? Will Quinn complete the first map of the whole world? Will Zain bring back enough treasure to satisfy the King? Will they win the race to the end of the world?