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.

Follows fifth grader Max as he searches for his best friend who disappeared, leaving behind a strange note.

"Told in multiple voices, after students from elite Brathelthwaite Boarding School and the Orphanage School compete in the Spindthrift Tournament, they team up to face the Whisperers"--Provided by publisher.