The Labyrinth of Gedref (S01E11)

When Arthur kills a unicorn, the most prized and mystical of creatures, Merlin's heart is filled with foreboding. The young sorcerer's concerns are soon validated when a curse descends on Camelot. With the fabled city fast running out of both food and water, Arthur is desperate to help his people. But to do so he must listen to the mysterious Anhora and he doesn't like what he hears. Will Arthur take Anhora seriously before it's too late? And if so, is he brave enough to face the challenges that are thrown at him? (BBC)