中世纪初，邪恶女巫魔甘娜率领大军攻打卡美洛王国，节节败退的亚瑟王与圆桌武士们最终靠著圣剑之力，将魔甘娜打入太空后才得以恢复王国和平，然而圣剑也因此消失踪影。1500年后的现代，魔甘娜带著外星科技重返地球，计画重组大军展开报复！多个世纪以来过著安稳生活的亚瑟与圆桌武士后裔们，有办法及时找回圣剑并对抗来自异星的强大威胁吗？
In medieval England, Merlin and King Arthur banish the evil enchantress Morgana and her son Mordred to the ends of the universe as Morgana vows revenge. In present day, Knights descendant Penn doesn"t take much stock in the legends of his supposed ancestors, even as the descendants meet in Thailand to practice fighting. But when Morgana and her son return to earth, armed with alien technology and hell-bent on destroying every last descendant of King Arthur and his knights, Penn must to come to terms with who he was born to be, and bring together the new Knights of the Round Table to save themselves and the earth from Morgana"s total vengeance.