Little is known of Lucy Walter whose son James was the oldest child of King Charles II. From those few facts, Goudge has spun an entrancing story of a vibrant girl whose great love for the prince—whose father ruled England, Scotland and Ireland as King Charles I—lasted a lifetime. We first meet Lucy as a child in Wales, where she lived with her family in Roch Castle and thought herself part buccaneer, roaming the countryside experiencing all of creation with a dazzling joy.

It was then she...