Eleven years ago, Tilly Nyx did something she wasn't supposed to. As a result, her mother was killed. Her village was destroyed. Her sister disappeared. An ancient horror sent her into hiding.Now sixteen and undercover in New York City, she has waited eleven years to go home, even though she doesn't know where home is or how to get there. All she has is the map that her mother made her swear to protect with her life. And the promise that a man called the Time Keeper is supposed to rescue her, if she can just hold on long enough for him to arrive.But when the Time Keeper is found dead in his hotel room, with a message to contact Tilly inked on his skin, her world is upended once again. Now someone is hunting for her and the map, and if they find her, the consequences will be deadly.Tilly soon finds herself plunged into the world where her story began-a world of oceans and sailing ships, of feuds between ancient magical families. She joins a fleet in search of the secret her map holds, which has been guarded by her family for four thousand years.As Tilly learns how to cast sprites and make potions, she and her three friends must follow the trail of murky, disturbing clues left by her ancestors before time runs out. But the closer they get to their destination, the more Tilly discovers that nothing is what it seems...not even herself.