The Changeling (S03E06)

Uther insists that Arthur marry the visiting princess, Elena, but Merlin grows suspicious when he uncovers that Elena might not be who she appears to be. As he delves deeper into her background, he discovers that her nanny is actually a Pixie. This revelation raises questions about their true intentions and who they serve. What do they stand to gain from Elena's union with Arthur, the future king of Camelot? With time running out, can Merlin unravel the mystery and save Arthur from what could be the gravest mistake of his life?