Historians have thought for centuries that King Arthur was only a myth, but the legend was based on a real hero, torn between his private ambitions and his public sense of duty. A reluctant leader, Arthur (Owen) wishes only to leave Britain and return to the peace and stability of Rome. Before he can, one final mission leads him and his Knights of the Round Table – Lancelot, Galahad, Bors, Tristan, and Gawain – to the conclusion that when Rome is gone, Britain will need a leader to fill the vacuum. Britain needs a king – someone not only to defend against the current threat of invading Saxons, but to lead the isle into a new age. Under the guidance of Merlin, a former enemy, and the beautiful, courageous Guinevere (Knightley) by his side, Arthur will have to find the strength within himself to change the course of history.