When Allashua disobeys her parents and goes fishing on the sea ice, she has to use her wits to escape the Qallupilluit--the troll-like creatures her parents have always warned her about that live beneath the frozen surface of the sea. But the only way to break out of their grasp is through an exchange: Allashua can go free if she brings her brothers and sisters back to the sea ice instead. Allashua doesn't want to give them up, but what can she do? After all, a promise is a promise.