Winchester, Wessex; Ragnar kisses Brida goodbye as she leaves on a horseback. Meanwhile, Uhtred and Gisela lay in bed together. She asks if Uhtred will kill her brother when they cross paths. Uhtred has sworn to Alfred that King Guthred won’t be harmed. Gisela wants to return to Eoferwic with him, but he won’t allow it.
Uhtred finds Ragnar gearing up to leave. He'd ask Uhtred to come with him but he’s already heard that Uhtred has sworn his sword to Alfred. Uhtred promises that he’ll be with Ragnar when the time comes. Alfred is sending him to kill Erik and Sigefrid. If he succeeds, then Guthred will be in Uhtred’s debt and he will demand the use of his men. Ragnar tells Uhtred that in swearing Alfred his sword, he’ll remain a slave. However, Uhtred will do whatever he has to in order to kill Kjartan.
Uhtred visits Beocca in the temple. He wants Beocca to marry him to Gisela before they ride off to Eoferwic. Uhtred loves Gisela, and so Beocca tells him to bring her to him and to be quick and discreet.
Æthelwold informs Uhtred that he’s been instructed to join him on his quest to Eoferwic by Alfred. He’s to be Alfred’s errand-boy. Æthelwold suspects that Alfred wants him dead, which is his reason for sending him along.
Father Beocca marries Uhtred and Gisela in the temple. He bounds their hands and they kiss.
Odda fears that should Uhtred survive his trip to Eoferwic that he won’t return. He believes Bebbanburg will hold a greater pull than Wessex. He will look towards Kjartan and continue his blood feud. Should Uhtred defeat Kjartan, Ælswith worries that Uhtred and Ragnar will hold power in Northumbria. Should that happen, Steapa has been put under instructions to kill Uhtred, Alfred explains.
Loidis; Northumbria; Uhtred, Ragnar, Hild, Finan, Æthelwold, Steapa, and Beocca head to Eoferwic. But first, they stop in Loidis, where they reunite with Brida. Ragnar is greeted by what's left of his Danish army. Rollo greets him with a hug. Brida explains that their men aren’t willing to fight the brothers for someone like Guthred. However, they’ll need his army to take Dunholm. Brida suggests killing the Northmen, then Guthred, thus allowing them to take Eoferwic. However, all Ragnar wants is his sister and Kjartan’s death. Given that the Northmen have an open camp, Finan suggests they only kill Sigefrid and Erik, rather than the brothers and their men. He suggests killing them while they’re sleeping.
Dunholm, Northumbria; Sven warns Kjartan that Uhtred and Ragnar are in Northumbria. He surmises they’ll go to Guthred for men. He’s certain that Uhtred will attack. Sven wants to hunt them down, but they’re safe inside the fortress. He then orders Sven to go to his wild white and tells her she need not feed her hounds.
Sven goes into the cellar and enters Thyra’s cage to inform her that Ragnar is in Northumbria and is planning an attack. Kjartan demands that she let the hounds go hungry. Thyra replies that she has no brother and tells Sven to leave.
Northumbria; Uhtred, Ragnar, Brida, Hild, Finan, Æthelwold, Steapa, and Beocca find Sigefrid and Erik’s camp. Brida and Ragnar don’t believe the plan is safe as there are too many uncertainties. They don’t even know which tent the brothers are in. Æthelwold informs them of the game Tafl. The king is positioned at the centre of the pieces. Æthelwold presumes the brothers are in the center.
Uhtred, Finan, and Steapa go in alone. They take out three guards. Uhtred enters Sigefrid’s tent. He is disarmed by Sigefrid’s woman, and then Uhtred and Sigefrid exchange blows. Uhtred cuts off Sigefrid’s hand and then drags him out the tent for all to see. Finan and Steapa stand by his side. Erik and Hæsten arrive. Sigefrid orders his brother to kill Uhtred, but Erik instead tries to bargain with him. Erik gives Uhtred his word that he is willing to pay whatever price necessary. He tells Erik to take one ship and leave Northumbria, never to return. Erik agrees to his terms and takes his brother and castrates his hand.
Eoferwic, Northumbria; King Guthred claims that he is glad that Uhtred was recovered. However, Uhtred killing him would be a mistake. Uhtred throws Sigefrid’s hand on the table. In return, King Guthred will ready his army. Or else he will kill Guthred for his betrayal. For what Guthred did to him and Halig, Uhtred can never forgive him. But, he’ll spare his life. Should the king fail, Ragnar will kill him and take Eoferwic for himself.
King Guthred asks Uhtred to join him. Admittedly, he is afraid of Uhtred. He also feared that Uhtred would take his newly found power. And for that, he made Uhtred a slave. Uhtred slaps him when he tries to explain how he spared him rather than killing him as his uncle ordered. He then asks about his sister. Uhtred replies that Gisela is his wife. Guthred will write to Alfred to inform him that Uhtred’s journey to Dunholm is his instruction. He hopes that one day, Uhtred will forgive him, as he considers Uhtred his greatest friend. Uhtred tells Ragnar that Dunholm is his to take and then calls Sihtric over and asks why he lied to him about Dunholm not having weaknesses. Uhtred saw a door along the east wall. Sihtric replies that Uhtred could never bring an army through it. Uhtred replies that he doesn’t intend to.
Dunholm, Northumbria; Uhtred, Ragnar, Brida, Hild, Finan, Sihtric, Æthelwold, Steapa, and Beocca lead an army of men to Dunholm. Ragnar and Brida take a group of men down the path. Rollo fears that the ram won’t work. Clapa replies that while it won’t force open the gates, it will work.
Uhtred, Hild, Finan, Sihtric, Æthelwold, Steapa, and Beocca arrive just outside the fortress. They send the signal for Ragnar and Brida to lead their army to the front gate. Clapa, Rollo, and the others form a shield wall and ram the front gates. Meanwhile, the others breach the East wall. Kjartan and Sven watch from above as they continuously try to force their way in.
They invade the fortress, killing many men. Steapa kills the guards by the gates and opens them for Brida, Ragnar, Clapa, and the others to enter. Kjartan tries to stop him, but he is unsuccessful. Rollo is struck by a spear and killed soon after entering the fortress. And Ragnar kills the man responsible. They eventually force Kjartan to retreat.
Hearing the battle above her, Thyra takes this opportunity to escape her cell. She leads her hounds upstairs, where they kill Sven.
Kjartan witnessed from outside the window as Sven is torn apart about Thyra’s hounds. Ragnar then challenges him to a battle to the death. Brida warns him against in, but Ragnar is fueled by revenge. He taunts Ragnar by telling him how often they would hump his sister and how they killed the rest of his family. Ragnar disarms Kjartan and pins his arm to the ground with his sword. He then kicks Kjartan’s sword out of his hand so that he doesn’t go to Valhalla. Ragnar finally kills Kjartan. However, after doing so, he continues to stab his lifeless body repeatedly. Even his own comrades watch in disbelief. Uhtred has to pull Ragnar off of Kjartan’s body.
Thyra exits with her hounds. She blames Ragnar and Uhtred for not coming to her rescue. She says that the price for her life is theirs. Father Beocca intervenes. He forbids her from killing Uhtred and Ragnar. He extends his hand and offers to help her. Thyra screams and runs back inside.
Beocca finds Thyra in her cell with her hounds. He introduces himself and explains that he’s known Uhtred since he was a boy. Beocca explains that Uhtred and Ragnar have wanted for so long to find her. She has God given strength, and he only wishes to help her. Thyra tells him to stay. She recalls when Uhtred saved her from Sven when they were younger.
Uhtred says goodbye to Ragnar and Brida, who are settling in at Dunholm. Himself, along with Finan, Sihtric, Hild, Thyra, Æthelwold, Clapa, Beocca, and Steapa leave for Wessex.