Orphaned as a young girl because of the imprudent marriage of her mother, Queen Katherine Parr, Mary Seymour vows never to fall in love-and under no circumstances will she marry. Lady Strange, her mysterious guardian, offers the young woman an extraordinary alternative to marriage: Mary is to become a white magician who will join Queen Elizabeth's court and ensure the success of the Virgin Queen's reign.

Accompanied by her magical hound, Perseus, Mary sets out to learn the properties of different stones and the art and precision of natural spells. Soon after her sixteenth birthday, she joins Elizabeth's court as a lady-in-waiting. Upon her arrival, Mary realizes that Elizabeth's court is rife with men and women who are vying for power. The most dangerous of all is Edmund Seymour, Mary's disturbingly handsome cousin. From the moment she meets Edmund, Mary has to fight her growing attraction, especially once she discovers that he is a black magician, the dark mirror of her own self. But, despite the threat Edmund poses to Mary, he seems to be the only one who truly understands her. When Edmund becomes involved in a plot against the Queen, Mary finds her beliefs tested in ways she never could have imagined.