Eighteen-year-old Liobhan is a powerful singer and an expert whistle player. Her brother has a voice to melt the hardest heart and is a rare talent on the harp. But Liobhan's burning ambition is to join the elite warrior band on Swan Island. She and her brother train there to compete for places on the force, and find themselves joining a mission while still candidates. Their unusual blend of skills makes them ideal for this particular job, which requires going undercover as traveling minstrels. For Swan Island trains both warriors and spies. Their mission: to find and retrieve a precious harp, an ancient symbol of kingship, which has gone missing. If the instrument is not played at the upcoming coronation, the heir will not be accepted and the kingdom will be thrown into disarray.