An ancient treasure-filled tomb is found but Gaius desperately tries to persuade the King to seal it up. He believes it belongs to evil sorcerer Cornelius Sigan who cursed Camelot and swore to return to destroy the city. But the King ignores Gaius, dismissing the story as a myth.

Arthur and Merlin’s relationship comes under threat when new servant Cedric turns the prince against his friend. Merlin does not trust the newcomer and he’s right to be suspicious. Thief Cedric is only after the jewel at the heart of the ancient tomb. But the conman does not realise how dangerous the treasure could be.

Merlin has to try and protect Camelot, but without his friend Arthur on his side it will be difficult. He’s forced to look to the Great Dragon for help, a creature he promised he would never trust again.