Elaine "Ellie" Harrison and her family have moved to Annapolis, Maryland, while her parents are on sabbatical. Ellie's parents are professors of Medieval history; they plan to do research in Annapolis on their separate interest, the Lady of Shalott and a sword which resembles the Arthurian Excalibur. Ellie is a 16-year-old junior in high school who is not thrilled about moving, but is used to dealing with her parents' eccentricities. Like when they named her Elaine, after Alfred Lord Tennyson's ill fated character the Lady of Shalott. Elaine of Astolat, in the poem, killed herself when Sir Lancelot chose to love Queen Guinevere over her. Ellie sees the poetic Elaine as a weak woman and is not thrilled to be named after her.

Ellie makes a few friends at school and finds herself pulled into the intriguing world of A. William "Will" Wagner, whom some believe is the reincarnation of King Arthur. Ellie and Will find themselves inexplicable drawn to each other. Both as friends and as maybe more. However, Will already has a girlfriend, the lovely and popular Jennifer — who just so happens to be cheating on him with his best friend, Lance. As Will and Ellie grow closer, Ellie begins to see things in their relationship she hadn't before. Will is almost convinced they knew each other in another life. As he tries to make sense of the changes taking place in his life, he believes more and more that he and Ellie have met before.

As Ellie enters Will's world, she becomes aware of things in his life that are eerily similar to the life of King Arthur: a cheating partner, a loyal but confused best friend, a deadly half-brother and dysfunctional parents. Ellie, with the help of her father's old sword and her World Literature teacher Ms. Morton, finds herself standing by Will's side as he faces down almost certain death at the hands of his brother and the forces of evil. A secret society has Will and Ellie convinced, almost, that Will is the second coming of Arthur and that he has been born to save the world from evil. Ellie and Will aren't sure about this, but they are willing to wait and see what happens.

The book ends with Will living at Ellie's house after his father has kicked him out. Ellie's parents are convinced Will is Arthur and now know that Ellie isn't a reincarnation of Elaine of Astolat, but of the Lady of the Lake. Arthur's magical protector. The end of the book is a set up for another volume in the series.