Cassie and her friends escape to Glastonbury, where they discover that their adventure has only just begun. At an inn they meet a mysterious woman who knows a few things the teens don't - about their own story. To thrust them forward to the next stage of their journey, she sends them backward in time. Passing through a musical "time slip" on horseback, sending the four friends to the kingdom of none other than King Arthur. There, Cassie meets her Brenwyd ancestors, who train her to use music to heal, to fight, and to discern good from evil. As a Brenwyd, Cassie can hear melody in ever living thing, as well as in the time slip itself. Its crescendo, which is quickly approaching, will give the teens a brief window of time in which to journey home. But before they can return and finish the rescue mission they began in their own era, they have a vital role to play in this one. To preserve the legacy of a kingdom that has fascinated imaginations for centuries, they must uncover several secrets, shed light on a false rumor, and battle the original Brotherhood - all before the slip reopens at the climax of its song. Caught in a race against time, will Cassie and her friends be able to find answers to their questions in time to save the kingdom... and themselves? Caught in a race against time, will Cassie and her friends be able to find answers to their questions in time to save the kingdom... and themselves?