The sons of Ragnar Lothbrok, the notorious Viking king, vow revenge on King Ælle of Northumbria for killing their father by throwing him into a pit of vipers. They gather a vast host of Danes and Norsemen to invade England and kill Ælle. However, for Ivar the Boneless, Ragnar’s eldest son and the leader of the Great Heathen Army, it is more about conquest than revenge.
After overrunning East Anglia they annihilate the Northumbrian army outside York. Ælle is captured and suffers the blood eagle, a horrendous way to die. Two young men - Ricsige, Lord of Bebbanburg, and his military tutor, Drefan - escape the carnage and must build a new army if their way of life is to survive.
Together they manage to preserve the old Kingdom of Bernicia – the North Eastern part of Northumbria – and hold it against both the Vikings and the Scots, who have long wanted to push their border south to the Tweed.
Whilst the Vikings battle against King Alfred of Wessex in the south and expand their territory across the sea in Ireland, Ricsige and Drefan manage to keep the banner of the Wolf flying in an independent Bernicia against all the odds.
When Ricsige is killed during negotiations with Halfdan - another of Ragnar’s sons and the ruler of the southern half of Northumbria - he is succeeded by his brother, an imperious and overconfident boy of twelve who ignores Drefan’s advice at every turn. Can Anglo-Saxon Bernicia survive?