It is recalled that in the 5th century, the Druid Merlin had helped the young Arthur to become king of England. But Merlin, the victim of the Morgan Fairy, had ended up trapped in a rock. Centuries later, in the middle of the Middle Ages, Merlin was released. He discovered that around him the situation has changed a lot. The men of An Mil no longer care about magic and everywhere the chapels of Christians replace the ancient dolmens. The small people of the fairies are dying, the dragons have almost disappeared, Ireland is invaded by the priests. With the help of a few pints of beer and the young Gwyned, descendant of Galahad, to whom he entrusts the fabulous sword Excalibur, Merlin will seek to break Christendom out of Ireland and to save a world of magic and enchantment gradually destroyed by the new beliefs.