Merlin Season 3 Episode 9

A healer is in Camelot,using magic to heal the sick,and Gaius quickly realises it is Alice,a woman whom he was about to marry many years earlier until she had to flee from Pendragon's persecution of magicians.Now Gaius is happy to work with Alice again in preparing potions but he is unaware that Alice is being controlled by a mythical monster,a manticore,which urges her to poison the cold-hearted king. To break the manticore's hold over Alice and ultimately save her from execution Gaius has to perform the magic that he possessed but had forsaken long ago.