When Merlin's village is attacked by Kanan, a fearsome raider, Merlin rushes home to help - and is surprised when Gwen, Morgana and Arthur insist on coming with him.
It quickly becomes clear that the odds are stacked firmly against them. With dozens of lives at stake, Merlin's old friend William forces him to make a difficult choice. Is he prepared to use magic to save the village, and in doing so reveal his sorcery to Arthur? Or will his destiny to protect the future King lead him to keep his magic a secret, which may mean leaving his old friends to die..?