Camelot

Using magic to disguise herself, Morgan poisons her father, King Uther. Inviting her father's most powerful enemy to Castle Pendragon, she formalizes an alliance. Merlin, Uther's most trusted adviser, finds a young man named Arthur, telling him he is of royal blood and the new king. Morgan hears of the "new king", believing it impossible, and that she is the rightful heir.

Arthur meets Guinevere, the woman of his dreams. Morgana and King Lot conspire to attack Camelot and take the throne. Lot personally mortally wounds Arthur's legitimate father, but the dying father gets his revenge by stabbing Lot to death before dying. Merlin has Arthur reclaim the legacy sword in the stone, known here as the sword of Mars, to prove his worthiness as king.

Guinevere's home is ransacked just before her wedding. She flees to Camelot to be protected by her husband-to-be, Leontes. 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 then meets up with Guinevere, struggling with their relationship as she readies for to marry Leontes.

Merlin sets off, seeking out a legendary sword-maker, Caliburn, to create a weapon worthy of King Arthur. However, the story spirals downward as Merlin accidentally kills Caliburn. His daughter, Excalibur, rows out to the middle of a lake, planning to throw the sword as revenge. Merlin lies to Arthur about how he obtained the sword, which he names Excalibur in honor of the sword-maker's daughter.

Arthur intervenes in a murder investigation convinced that the killer may have had an honourable motive. Arthur tries to establish the rule of law and begins a trial. Morgan tries to cultivate political favour by promoting herself as a champion of justice while framing a local mercenary for the beating of the nun who raised her. Morgan then slits the mercenary's throat in front of her followers.

This episode interweaves three stories: Guinevere's journey to her parents' home where her father is dying, accompanied by Arthur, Kay's journey (at the behest of Merlin) to his deceased father's home to retrieve his library, and a woman who comes to Morgan for justice claiming that the nun Sybil caused the death of her daughter as result of deliberately setting fire to the convent.

Morgan invites Arthur and his regiment of soldiers over for an evening's entertainment and an overnight stay. During this time, she sets up a series of intrigues and hoaxes which include a faked attack on the castle, which many believe is by a former rival of Uther. At the end of the episode, Morgan has shape-shifted to look like Igraine and rides back to Camelot with Arthur in Igraine's form.

Igraine is held prisoner at Morgan's castle, Pendragon, while Morgan, magically disguised as Igraine, roams the halls of Camelot plotting intrigue. As Igraine, she reveals to Leontes that Arthur had a tryst with Guinevere in the morning before their wedding. The real Igraine eventually escapes Morgan's castle, traveling back to Camelot only to run into Morgan, still in Igraine's form.

Morgan convinces Igraine that she is just hallucinating and escapes Camelot. When Merlin and Igraine confront Morgan at her castle, she and her followers arrest them. She then stages a raid at Bardon Pass, hoping that Arthur will be inadequate to stop it; positioning her to become known as the better ruler of Camelot, and proceeds to travel to Camelot with her new prisoners, Merlin and Igraine.

Morgan's plan to overthrow Arthur is exposed. Leontes dies protecting Arthur at Bardon Pass, and tells him to treasure Guinevere. Morgan claims Arthur has died, after which Sybil says she should be Queen, which the people agree with. Arthur returns at her coronation and reveals one of her men, who claims she was behind it.