Gwyn has never wanted to act like a lady. She much prefers fighting with her wooden sword to weaving intricate tapestries. When her father takes her to join the royal court at Tintagel, Gwyn meets Merlin: a wild young boy with unique powers, in desperate need of her help. They flee Tintagel together, and before long, the young prince, Arthur, joins them. So begins an epic journey across ancient Britain, involving giants, mermaids, unicorns and witches - and their discovery of a truly monstrous plan.