Morgan returns from exile and takes her revenge. Merlin retrieves Arthur from the family he was fostered with, and convinces him to claim the throne.
Arthur is crowned King of the Britons and Morgan and Lot have a falling out. Morgan decides to turn to other "dark" methods of gaining what she wants even at a price.
Kay and Leontes seek out a trusted new warrior to join them. Arthur and Merlin accept an invitation to join Morgan at her castle for dinner. Arthur is forced to concede defeat in his pursuit of Guinevere
Merlin sets off on a journey to find a sword suitable for a king by seeking out a legendary sword maker. A conversation with Guinevere changes Arthur and he begins to assert his power by sparring with Leontes.
Arthur creates Camelot's first tribunal of justice which takes shape through a battle of wills, not blood. Aided by Sybil's cunning, Morgan reaches out to the townspeople in her pursuit to take back the throne.
The men of Camelot discover the territory beyond the castle is filled with danger and disorder. Arthur hears Guinevere has ridden out alone to see her father and goes after her to protect her on the journey.
Morgan puts on a feast for King Arthur and his Knights at Castle Pendragon which turns to panic as the castle comes under attack. As Arthur and Morgan's men join forces to fight, Merlin believes a plan is afoot.
Pursuing the power of her dark magic, Morgan hides in plain sight at Camelot where she begins her plan to drive a wedge between Arthur and his men. Igraine tries to find a way out of Castle Pendragon.
Arthur and his men learn of an attack at Bardon Pass and ride out to defend it. Merlin realizes he's been seduced by a shape-shifting Morgan. The men begin to lose faith in Arthur after learning of his betrayal.
Arthur struggles to defend himself against the mercenaries on Bardon Pass. Morgan leads Sybil and her followers to Camelot where she receives information that leads her to believe the throne is within her grasp.