When Freya is brought back to life, mistaken for a noblewoman and close friend of Camelot, pushed by King Uther into a marriage with an also less than willing Arthur, Merlin finds himself being set up to commit the ultimate act of treason. Because of his magic, he's used to committing treason against Uther's rules, but not betraying Arthur. Merlin/Freya/Arthur & some Arthur/Gwen.