Merlin - Season 2 Episode 1
The Curse of Cornelius Sigan

New servant Cedric muscles in on Merlins position as Arthurs right-hand man, and turns the prince against his loyal friend. Merlin is convinced the slippery newcomer is up to something, and he is right - Cedric is a conman and a thief who is after a magnificent jewel, recently unearthed in a tomb far beneath Camelot. Little does he know, his precious prize is more dangerous than he could possibly imagine. Camelot has never been more vulnerable, but how can Merlin make things right when, thanks to Cedric, he might have lost Arthurs friendship for good? Merlin faces the prospect of turning to the one creature he swore he would never trust again - The Great Dragon.