On his ninth birthday, Gwyn Griffiths is bestowed with five special gifts infused with ancient Welsh magic; he tries to use the magic to help him find his sister Bethan.

Gwyn investigates the identity of the pale girl in Arianwen's web; his magical powers are putting a strain on his relationships with Alun and his parents.

When the secret of Gwyn's magic spills out, the school bullies are onto him; he finds an unlikely savior in Pendewi's new pupil, the mysterious Eirlys.

Gwyn searches desperately for his missing Snow Spider; when he releases the dreaded toy horse, a deadly storm falls on Pendewi, unleashing the monster of Mabinogion legend.

With his Snow Spider safely returned, Gwyn ventures to battle Efnisien; unknown to him, Eirlys and Alun have followed him.