Merlin Season 2 Episode 13

Morgana has gone with Morgause and the dragon, freed by Merlin, repeatedly attacks Camelot, causing huge fire damage. Only a dragon-lord is capable of containing the beast and Pendragon persecuted these men years earlier and only one still survives, Balinor, who lives like a hermit in a cave. Gaius, who helped him escape Camelot, tells Merlin this is his father and when Merlin and Arthur trace him, Merlin reveals himself to Balinor though they keep it from Arthur. Balinor agrees to come to Camelot to assist but there is further drama before Merlin proves himself to be his father's son and defeats the dragon.