Uther, the High King, has died, leaving the infant Mordred as his only heir. His uncle, the loyal and gifted warlord Arthur, now rules as caretaker for a country which has fallen into chaos - threats emerge from within the British kingdoms while vicious Saxon armies stand ready to invade. As he struggles to unite Britain and hold back the enemy at the gates, Arthur is embroiled in a doomed romance with beautiful Guinevere. Will the old-world magic of Merlin be enough to turn the tide of war in his favour?