Uther Pendragon is dead.
Ygerne is pregnant and Merlin is taking care of her and her little girl Morgane. Together, they take refuge in King Erin's castle.
But father Patricius, haunted by the prophecy of the new king, wants to have Ygerne assassinated before the child-king is born and therefore stop the prophecy from coming true.
The castle is under siege. Arthur is born but Ygerne dies. Merlin must make a choice, he abandons Morgane to save Arthur...