Seventeen-year-old Gwen is settling into her new home in Oregon and looking forward to senior year when she is kidnapped by Kian, who warns her that she is in terrible danger. An ancient war was fought between magical Celtic warriors and three evil magicians. Those magicians are alive and well and need Gwen's magic to regain their power. If they succeed, they'll be unstoppable. To save the world, Gwen must unlock the magic trapped in her memories of a past life in Britannia.

As Gwen starts to recover her lost memories and awakens to her power, she suffers the consequences of a divided soul. Gwen and Kian travel to New York and then to England to find others of her kind. Gwen, Garrison, Seth, and Moira need each other to solve the puzzle of their last days in ancient Britannia. They are only as strong as what they remember, but a troublesome history threatens to doom the world. One way or another, a deadly showdown is inevitable, ready or not …