Merlin becomes a deadly weapon in Morgana's fight for supremacy when he falls into her hands. By recurring to ancient magic, she manages to turn friend against friend and creates the perfect assassin out of the young sorcerer which puts an oblivious King Arthur in great danger. Will anyone notice Merlin's unusual behaviour before he is able to do any serious harm to the King?

Morgana joins forces with enigmatic wizard Alator to uncover a secret that could change the course of destiny, as the magical drama continues. With allies on both sides of the castle walls, can anyone stop her before Merlin's greatest secret is revealed?

Morgana and Helios have successfully captured Camelot, and Merlin and Arthur are outlaws on the run, in the last episode in this season of Merlin. Trapped in Ealdor with a ruthless army closing in, their situation becomes desperate. Arthur must take control before Camelot is lost forever… But faced with Agravaine’s betrayal and the strength of Morgana’s force, the young King has lost his conviction. Only Merlin can restore his faith, and only an extraordinary act can prove to the King that he was born to rule. Will the young warlock convince Arthur before his dreams of Albion fall to pieces?