The Dragon's Call (S01E01)

Merlin, a wizard on the cusp of adulthood, arrives in Camelot hoping to find a use for his burgeoning talent for magic. He is welcomed by Gaius, the court physician, but Merlin soon learns magic has been outlawed by King Uther, the tyrannical leader of the realm, its practice made punishable by death. When the Great Dragon summons Merlin to his cave, he tells the young wizard that he has a great destiny - to use his skills to keep the young Prince Arthur safe. But Merlin hates the flashy, arrogant Prince, and Arthur despises the wizard with equal fervour. So when an evil witch threatens Prince Arthur's life, Merlin finds himself tested - will he face up to his destiny to keep Arthur safe? And can he do so without getting caught? (BBC)