A kid pulls a sword from stone and thinks that makes him king. It doesn't. The real fight is against an enemy he can't just swing Excalibur at, so he has to learn what kingship actually costs. Merlin knows this from the start. The show builds something most fantasy adventures skip over: the space between destiny and earning it, between a chosen one and a real leader.

Arthur grows up unaware of his royal blood until the day he pulls Excalibur from its stone, a feat no one else can accomplish. The sword marks him as Britain's rightful king, but the evil King Lavic, backed by the witch Medessa, stands in his way. Merlin tells Arthur that he must find the Holy Shield to defeat them, sending him on a quest to seek it. Along the way, Arthur meets four young knights who share his ideals: Lancelot, Perceval, Tristan and Guerrehet. Together they travel from country to country, helping common people oppressed by nobles under Lavic's sway and putting down bandits, all in pursuit of rebuilding the ideal Kingdom of Logres.