This is Book 5 of the Saxon Chronicles.
Somehow, Cornwell continues to find ways to test the loyalties of Uhtred of Bebbanburg. Wounded deeply by his own personal tragedies, Uhtred violently shakes himself free from the bonds of his oath to Alfred and once again seeks the refuge of the north. It is there that he finds himself among allies and enemies alike, involved in a plot to do what has never been done before, to do what he has endured blood and battle to prevent: Uhtred plans to aide the Danes in the conquest of Wessex.
But the fates were kind (or cruel) enough to remind Uhtred of an earlier oath, sworn to one that he would willingly and without hesitation give his life to defend. And so, once again, Uhtred finds his steps turning south. In order to protect those that he loves, he must also turn his back on others that he loves as well.
Everything that made the last four books great is present here as well. My only complaint is that it had to end. Fortunately, this is not the end of the series as Cornwell has promised that Uhtred and his blades will be needed yet again. There is still so much of this story left to tell, and I look forward to seeing where Uhtred's wandering path will lead him next.