A new threat appears, Ragnall Ivarson, brother of Sigtryggr who is married to Uhtred’s daughter Stiorra, has been expelled from Ireland by the natives and is leading his Northman army to Mercia. They landed near to Ceaster where Uhtred has a fortress, and Ragnall was not alone, it also came with a crew of Irishmen led by Conall, Finan’s brother, and Jarl Haesten, a well-known troublemaker.

Æthelflaed, the ruler of Mercia, sends reinforcements to stop the invasion, but Ragnall captures a partially built burh and demands the Mercia troops to capitulate and cede Ceaster to him. Uhtred is responsible for the defense and knows that Ceaster fortification is strong and well-built and that Ragnall would lose many men to take it.

Ragnall unexpectedly leaves Mercia and rides North, entering in Northumbria, which is in a weaker position ruled by a weak King. Uhtred realizes Ragnall’s intention and attacks the men in the rearguard, he knows that they will have trouble with Ragnall again, but he is happy that he left Mercia.

Heasten was left in charge of the partly built buhr, Eads Byrig, and he tries to convince Æthelflaed that he wants to surrender to her, claiming that he and most of his men are Christians. However, Uhtred knows that Haesten’s word has no value, and he discovers that Heasten only intends to buy time while Ragnall recruits Northumbrian men. Uhtred decides to attack Eads Byrig buhr, and he captures it, and he wants Æthelstan to fight Haesten, even with the disapproval of Æthelflaed and her priests. Uhtred proves that Haesten was lying all the time, and Æthelstan executes the sentence.

Ragnall returns with a bigger army, and he seeks for revenge, and he is not alone, Brida, that once was really close to Uhtred now has joined Ragnall and now hates Uhtred for choosing the Saxon side. Ragnall kills 42 captives in front of Uhtred, one for each man killed in Eads Byrig, and gives one alive: Father Judas, Uhtred’s elder son, that has been castrated by Brida.

Uhtred convinces Æthelflaed to let him do a surprise attack and catches Ragnall’s men unprepared, killing many of them and capturing horses, women and children. Ragnall is forced to split his forces, a small part goes north to ensure that Northumbria remains under his control while Ragnall and the rest of his men go deeper into Mercia pillaging and destroying.

Uhtred receives information that his daughter and son-in-law Sigtryggr are besieged in Ireland because they didn’t support Ragnall. Uhtred disobeys Æthelflaed and sail to Ireland to rescue them, and he offers to make Sygtryggr the king of Northumbria after defeating Ragnall, this move also would help Uhtred with his journey to recover Bebbanburg.

After leaving Ireland, they head to Eoforwik pretending to have Stiorra as a prisoner, they get through as Ragnall wants her as his fifth wife, and then they find Brida in charge. She is not only in charge of Eoforwik, but is also trying to eliminate the Christians - killing many of them crucified. Uhtred defeats her and lets Stiorra kill her, they also free all the hostages.

Uhtred takes his men and goes to find Ragnall, he sent a message to Æthelflaed requesting her to bring her forces, Uhtred plans to trap Ragnall between both armies. However, her commander doesn’t follow Uhtred request, and Uhtred ends trapped and outnumbered in the ruins of an old Roman fort.

Before the battle starts, Finan challenges his brother to a duel. He first kills his brother champion easily, but Conall refuses to fight and when Finan turns his back, Conall attacks, but Finan is agile and beats his brother, Finan takes Conall’s crown, make sure that the enemy sees it and heads back.

Uhtred makes then the next move, asking Sigtryggr to bring and set free eight women that Ragnall’s had taken hostage. Ragnall kept his authority using fear, and these two actions change the loyalty of many men, Ragnall orders the army to attack, but only half accept his order. Uhtred sees then the change to win, and orders his men to leave the fortification and charge, this last move completely dismantle Ragnall’s army and his men turn against him, and he is then killed.