Uhtred has been named Lord of Rumcofa (Runcorn) and helps protect the borders of Mercia whilst raising Æthelstan to manhood and training him to be a warrior.
In Iceland, Brida has become the leader of a fanatical band of Danish warriors who follow her and her young daughter Vibike, now a Seer.
Stiorra, having escaped with her attendants into the old Roman sewers below Eoferwic, is forced to watch as Brida tortures and sacrifices the women of the town.
Seeing his own family's influence waning, Lord Aethelhelm seeks to foment war between Wessex and Northumbria by encouraging Edward to attack Eoferwic without Mercian assistance, forcing the king to rely on him for money.
As the Danes make the square and the two face off, Uhtred, Sigtryggr and his men enter the city and free the captive locals, then launch an assault on the invaders, aided by the soldiers of Wessex.
Rǫgnvaldr, seeing the tide of battle turn, attempts to gain favour with his brother by joining Sigtryggr, but he is captured and imprisoned.
Edward attempts to placate the people of Mercia with penance for the death of the Ealdormen and fasting, meanwhile news of the slaughter at Aylesbury reaches Eoferwic.
Queen Ælfflæd, seeking solace in her faith as she sees her marriage to Edward fail, secretly travels north to Lindesfarne in the company of a Christian visionary named Aalys.
Uhtred and his men desperately try to uncover the truth and prevent more bloodshed, but both Sigtryggr and Edward prepare for battle, encouraged by Aethelhelm who still does not know he ordered his daughter's death.
When he finally discovers Ælfflæd's death, a devastated Aethelhelm contemplates suicide until his lieutenant persuades him to continue his plan.
Sigtryggr's forces discover Aethelhelm's army before Uhtred can reach them and they mount a dawn raid across a frozen lake, surprising and slaughtering the Saxons.
Uhtred tries to fight his way to Sigtryggr to stop the attack, but Edward arrives and, seeing his own troops slaughtered, leads a counterattack which breaks the Danish forces.
Aethelhelm manages to escape and heads for Scotia, hoping to continue his plotting to put his grandson Ælfweard on the Saxon throne.
Unable to leave Eoferwic in case the locals revolt again, Uhtred proposes that Stiorra be installed as Queen in order to maintain stability and pacify the Danish population.
Edward however declares it a sign from God, and weds her immediately, much to the disgust of Ælfweard who sees it as a betrayal of his recently deceased mother.
Outside Eoferwic, Brida ambushes a Saxon patrol and sends the survivor back with a message for Uhtred to meet her at Leodis.
In return, Constantin will wed Aelfwynn, claim half the riches of Mercia and a stake in its royal house and gain an assurance that no further Saxon advances will be made into the North.
On the road north the army encounters Cynlaef, who advises them that King Constantin has been spotted boarding a ship, but the thought of him braving the treacherous seas to come to Bebbanburg are dismissed.
Learning that his army is close, Constantin orders a general retreat from the walls, allowing dozens of defenders and civilians to escape by the sea gate, including Hild and Aelfwynn.
Stiorra, although she wishes to help, considers the battle lost and prepares to retreat but Uhtred appeals to her and her forces, promising that if they succeed Northumbria will become a new Danish homeland just as their ancestors intended, a place where Saxon and Dane can live together in peace.
As Edward and his army are slowly pushed over the cliff edge, Uhtred and Stiorra lead the Danish reinforcements to take the Scots in the rear.
Uhtred, however, reluctantly reveals he has come to an agreement with Constantin: in return for an exchange of hostages including Aldhelm, the Scots king will give up his claims to Northumbria.