Percival is a young boy who lives in isolation with his grandfather at the top of a mountain, far from the kingdom of Britannia. His life changes when a mysterious knight shatters his peaceful existence and forces him to leave his home and discover the wider world. During his journey, Percival learns that he may be one of the Four Knights of the Apocalypse, figures foretold by prophecy as being capable of bringing about the downfall of the kingdom of Camelot. Joined by new companions, he becomes involved in a conflict connected to King Arthur, the former heroes of Britannia, and powers that once again threaten the balance of the world.