Thirteen-year-old Carl leads a normal life, but one day a schoolmate takes him to the forest and shows him a mysterious gate that leads to the world of King Arthur and the Knights of the Round Table. Carlos is captivated by this chivalric world, full of adventures, where he has the opportunity to meet famous characters like Galahad, Lancelot, and Perceval, and where he himself will be knighted and adopt the name Sir Karel of Northumbria, participating on the search for the Holy Grail and experiencing adventures that will teach him the value of friendship and help him mature.