Roberts treats readers to entertaining tales that revolve around a quest to free the trapped souls of three Celtic demigoddesses. Legend states that they must be freed by three mortal women. Thus, three women get an invitation for cocktails and conversation that reads in part, "you are the key, the lock awaits." They are three very different people with different talents and strengths but, ultimately, strong wills and a determination to succeed unite them. Though the women frequently appear in one another's story, each book centers on one of them. In the first book, Light, the scene is set as readers meet the key players. The book then focuses on Malory, whose strength is an eye for beauty. In Knowledge, Dana's passion for books is a vital part of her story. In Valor, Zoe completes the quest and finds her special key. Readers are never really in any doubt that the women will be successful but that doesn't matter. How and where their key is found and how they get to know themselves better in the process make for entertaining reading.