The opening of the episode traces the history of the world. There was a silver age, a gold age, a bronze age, a dragon age, a giant age, so on and so forth. Now, the world is in the Iron age, otherwise known as the Human age.
After the opening, we see a young girl praying to the guardian star of her village for courage. During her prayers, the army of Drwc invades the cillage, taking control. The high priest orders the soldiers to start fires to draw out the villagers, only to be told by the young woman who was praying to stop. After she tells them that all the villagers are away from the villager, It is revealed that she is the top oracle priestess of Erin, daughter to Pwyll, king of an ancient kingdom, Albion. The high priest tells the young woman that he has found a way to ressurect the ancient demon king: to sacrifice her.
The scene shifts to the men of the village, who are off hunting bears, and a young man named Arthur defeats a large boar. In a quick shift back to the young woman, she threatens to kill herself before they can kill her. The high priest then reveals that he has two children of the village hostage, who call the young woman Riannon. He tells her that if she kills herself, he'll kill the children. She says that her name is Riannon, but the high priest is not satisfied; he wants the name that holds her magical powers.
Arthur and the other men return to the village shortly after the high priest and his army leave. The two children let Arthur know about Riannon's kidnapping. The men of the village vow to take back Riannon, who Arthur calls his sister, and daughter of the late chief.
The priest and his army are going through the ritual to revive the demon king, who the priest call Arawn. Outside, Arthur and the men arrive, only to see heavy guard outside the ritual cave. Under the cover of darkness, Arthur and his men take down the guard and enter the cave, fighting their way to the ritual room. Before they can arrive though, the priest begins summon the demon king. A mysterious onlooker says it's too soon as a beam shoots from the heavens to the demon king's coffin.
Through a series of events, Arthur is forced to go on by himself to the ritual room, where the demon king is rising from his coffin. The priest offers Riannon as a sacrifice to achieve his ends of becoming king of the world. As Arthur arrives, the demon king takes human form, and proceeds to Riannon. The episode ends with him standing directly infront of her, and Arthur running towards her.