Merlin is told by the Great Dragon that it is his destiny to make sure that the young Prince Arthur is kept safe. Anybody caught performing magic is punished with death and Merlin is not a fan of Arthur. When Arthur's life is endangered Merlin finds himself tested.

Merlin is saved from a terrifying winged beast by a heroic stranger- a young man named Lancelot, who dreams of becoming a Knight of Camelot. In order to thank him, Merlin provides falsified records of Lancelot's noble birth and Lancelot is accepted. However, with the winged beast- discovered to be a Griffin- still on the loose, Merlin's decision could have far-reaching consequences not just for Lancelot but for Camelot...

Morgana has a nightmare and sees Arthur's death at the hands of a strange but beautiful girl. Meanwhile, hunting in the forest, Merlin and Arthur save the same girl, Sophia, and her father, Aulfric from attack by bandits and bring them to Camelot for refuge. Morgana realizes that Sophia is the girl from her nightmare and tries to warn Arthur, who is smitten with her. As the truth of Morgana's magical gift for seeing future events unfolds, so does a father and daughter's plan to bring down the kingdom of Camelot by sacrificing Arthur in return for eternal life.

Uther's past comes back to haunt him as a mysterious Black Knight interrupts Arthur's coming-of-age celebrations, throwing down his gauntlet and challenging the Knights of Camelot to combat. The Black Knight, seemingly unstoppable, makes easy work of his combatants. But who is the Black Knight, and why is Uther so uneasy?

For the first time in over 300 years the fires of Idirsholas burn and Gaius is worried that a sorcerer has revived the deadly Knights of Medhir. Morgause returns and is determined to end Uther's reign at Camelot.

The Great Dragon is finally free. Full of rage, he attacks Camelot with pitiless intensity. The castle is crumbling and Arthur's men cannot hold out much longer but only a Dragonlord can kill a dragon and Uther wiped them all out years ago. Or did he? Gaius admits one such man could still be alive and in hiding.

The last Dragonlord is the key to Merlin's own past as well as the future of Camelot, but will Arthur and Merlin find Balinor in time to save the kingdom?

With the help of the Great Dragon, Merlin manages to return to Camelot only to find out that is it on the verge of invasion: Morgause and Cenred have teamed up and plot against a weakened Uther. Cenred's initial reluctance is won over by the fact that they count on an ally within Camelot walls who will ensure the castle is taken. Uther is unable to rule which forces Arthur to step up front and defend the citadel agains Cenred's powerful army. With the help of Morgause and to make things worse, Morgana plays a deadly card and summons a skeleton army to wreak havoc within the castle walls. Camelot's fate rests once again on Arthur's shoulders and Merlin's magic as they fight in their own way to hold off both an army of the living and an army of the dead. Will they manage to succeed?