Erin's family have an important responsibility: caring for the Toda, fearsome water serpents who form the core of their Lord's army. So when a number of Toda mysteriously die, it is Erin's mother who takes the blame, and the punishment - she is sentenced to death. Before she dies she manages to use an ancient, forbidden power to send Erin to safety - leaving her daughter alone, far from home but with the knowledge that both she and her mother are somehow different.

Soon, Erin finds she can talk to both the terrifying Toda and the majestic Royal Beasts, who protect the supreme queen of her realm. This knowledge gives her great power, but it also involves her in deadly plots and political gameplaying that she wants no part of. Can Erin save herself and prevent her beloved beasts from being used as tools of war, or is there no way of avoiding the terrible battles to come?