It is the year 1575 and young Willow Hawker, who lives in a small community of witches, is on the cusp of turning 13. Willow is about to undergo a pagan ceremony to enhance her witch powers, but she has serious doubts about it because she has never felt like a witch, for, unlike others in the tiny hamlet, she has never been able to perform any spells - apart, that is, from being able to mentally communicate with an old Willow tree. To add to her feeling of alienation, Willow looks nothing like anyone else in the hamlet, named Sanctus, for she alone has white blond hair and eyes of cornflower blue. Even in her own family Willow has always felt like the odd one out, not helped by an unresolved mystery concerning a twin brother she once had, named, Lark, who simply vanished one day many years previously. Whatever happened to Lark, his body was never found but for Willow, his memory is ever present along with a burning desire to find an answer as to what happened to him. Right before Willow's impending ceremony, her mother, Sorrel, reveals something to Willow that immediately diverts Willow's attention away from the Pagan ceremony, to a fabled place named, Asgard, home of the Norse Gods and to something that suddenly links her to the old Willow tree and with the trickster God, Loki...