In a clash of heroes, the kingdom is born. At the end of the ninth century, King Alfred of Wessex is in ill health; his heir, an untested youth. His enemy, the Danes, having failed to conquer Wessex, now see their chance for victory. Led by the sword of savage warrior Harald Bloodhair, the Viking hordes attack. But Uhtred, Alfred's reluctant warlord, proves his worth, outwitting Harald and handing the Vikings one of their greatest defeats. For Uhtred, the sweetness of victory is soon overshadowed by tragedy. Breaking with Alfred, he joins the Vikings, swearing never again to serve the Saxon king. Instead, he will reclaim his ancestral fortress on the Northumbrian coast. Allied with his old friend Ragnar - and his old foe Haesten - he aims to invade and conquer Wessex itself. Yet fate has different plans. The Danes of East Anglia and the Vikings of Northumbria are plotting the conquest of all Britain. When Alfred's daughter pleads with Uhtred for help, he cannot refuse her request. In a desperate gamble, he takes command of a demoralized Mercian army, leading them in an unforgettable battle on a blood-soaked field beside the Thames.