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?
Merlin is a young warlock who arrives in the kingdom of Camelot after his mother arranges for him to stay with the court physician, Gaius. He discovers that the king, Uther Pendragon, has outlawed magic and imprisoned the last great dragon deep under the kingdom.
The dragon tells Merlin that he plays an important role: to protect Uther's son, Arthur, who will bring forth a great kingdom. When Merlin meets Arthur, he believes that he is arrogant and Arthur, likewise, views Merlin as subservient. Merlin must keep his magic secret or face being executed by Uther.