Alex is given Excalibur by his mysterious archaeologist godfather on his 13th birthday. He is the prophesied Midwinter Child and he must save the world.
Alex is a normal 13 year old boy. Until on his birthday, four days before Christmas, when everywhere is under deep snow, he opens the present from his godfather. It is a magnificent sword.
But Alex is in danger because the sword is Excalibur and he is the heir to King Arthur. His parents have disappeared and he is alone in a snowbound world.
With the help of his best friend Callie he runs from the menacing Watcher in black, fleeing first to London to try to meet up with his godfather, Uncle Max, and then to Glastonbury.
He must find the lost magical scabbard that the witch Morgana tricked King Arthur out of in order to save his parents' lives, and he must outwit the forces of the Dark and the corrupt Minister of Defence who wants the sword for himself.
And in doing so he must journey to another world - to Avalon.