S3, E2: Whilst Merlin heals from the Serkets poison, Morgana and Morgause continue with their evil plan. They have mentally incapacitated Uther and convinced his enemy, Cenred, to invade Camelot. The fate of the kingdom now rests on Arthurs shoulders. The Prince and his knights resist the invaders, but what tricks do the witches have up their sleeves? Can Merlin stop Morgana in time to save Arthur from the enemy within?