Episode 1High King Uther banishes his son Arthur, who rescues a dying boy named Derfel. Arthur entrusts Derfel to Merlin and Nimue. Years later, Uther has a new heir, but Merlin has a dark vision for the future.
Episode 2
E2
Episode 2An untimely death leads Merlin to locate Arthur and urge him to come back to Britain; chaos ensues when Gundleus assaults Avalon.
Episode 3
E3
Episode 3Arthur takes Gundleus prisoner. Nimue struggles with the trauma of her rape and plans to kill Gundleus. Arthur learns that Gundleus' uncle Gorfydd is preparing for war. Nimue tries to pull Derfel into her plans, but Derfel can't betray Arthur.
Episode 4
E4
Episode 4Bastard son Arthur returns to the land he's been banished from to find a kingdom in chaos. Seeking the aid of his oldest confidants, Arthur aims to right Britain's path as he faces the most unexpected of obstacles.
Episode 5
E5
Episode 5Derfel feels uncomfortable about the attack on the mine – which Owain is keeping a secret. Nimue is discovered by Merlin who helps heal her. Tristan arrives demanding retribution but Owain denies his guilt.
Episode 6
E6
Episode 6Arthur and the tribe kings enter peace talks. Arthur suggests that as a show of faith, he marry Gorfydd's daughter, Ceinwyn. She is horrified by the news. Arthur and Derfel travel to Powys and rest for the night by a lake.
Episode 7
E7
Episode 7A line-up of activities are set for the nights before Arthur and Ceinwyn are to be married. Arthur is increasingly drawn to Guinevere; they meet secretly and kiss. Gundleus attacks Derfel but Derfel prevails. Arthur breaks the betrothal with Ceinwyn.
Episode 8
E8
Episode 8Arthur believes Bedwin will be able to negotiate peace with Gorfydd. However, when Morgan and Derfel arrive in Powys, they discover Bedwin being crucified. A Christian mob accuses Nimue of poisoning them. They demand justice from Arthur.
Episode 9
E9
Episode 9Derfel and Morgan take Bedwin's body back to Arthur. Ceinwyn reveals that Gorfydd is allying with the Saxons. Derfel discovers that the Christians died of natural causes, but Arthur reveals he has exiled Nimue to the Isle of the Dead.
Episode 10
E10
Episode 10Derfel makes his assault on the Isle of the Dead and finds Nimue. Arthur meets the Saxon King Aelle and hands over information which will benefit their advance into Britain. In return, the Saxons will not attack Dumnonia for an agreed period of time.
