Merlin: Enemy from within (Sequel to the return of Morgana)

Arthur, Gwaine and Gwen now know Merlin's secret. However is that a good thing? Merlin nearly came close to death but Morgana and Morgause are still out there. Maybe things will be easier for Merlin now that his secret is known but there is much for him to learn before he becomes Emry's. However while everything seems fine it is not. The enemy has decided to attack Camelot from within but who is it? How are they doing it? Who is in danger? This is Merlin's toughest enemy yet because he doesn't actually know who it is or what they want until it's too late.