Newly crowned Queen Catrina settles in as Camelot's first lady. As her true troll nature surfaces, her influence over Uther increases, and the repercussions are felt throughout the kingdom.

When Catrina accuses Merlin of stealing, he is forced into hiding. Forced to sneak around the castle, Merlin must find a way to expose Catrina's true form without getting caught and beheaded. Even if he succeeds, is it enough to break her powerful magic? Or will Camelot be stuck with a troll queen forever?

When a mysterious warrior challenges Arthur to a duel, no one could possibly predict the devastating chain of events that is set in motion - least of all the young prince himself.

Arthur and Merlin soon find themselves on a strange quest at the behest of the beautiful Morgause. Through her, Arthur discovers a dark secret which threatens to bring about the downfall of the kingdom.