Rollo battles Ragnar when Jarl Borg and King Horik's men clash. Rollo surrenders to Ragnar after admitting he cannot kill him. Ragnar negotiates an unsteady truce between Borg and Horik, then returns to Kattegat. Ragnar's attempts to reconnect with his wife are hampered when Lagertha learns about his affair with Aslaug. Ragnar finally mourns for his dead daughter, Gyda. Ragnar's life becomes more complicated when a ship arrives bearing a visibly pregnant Aslaug. Rollo is placed on trial, but is
Four years later, Ragnar is married to Aslaug and has two sons, with a third child on the way. Ragnar finally announces plans to raid England. Horik and Borg arrive, but Horik persuades Ragnar to break the pact with Borg. Ragnar accepts Rollo back into his family, but forbids him from raiding. Aslaug thinks that Ragnar treats her as an idiot and prophesies to him that their next son would be born with a serpent in his eye. The Seer tells Ragnar that his sons will be more famous than him. Ragnar
Ragnar and his men move deeper into Wessex. He believes the land's greatest wealth is its rich soil, which could support a Viking colony. Ecbert sends envoys to ask Ragnar to leave; Ragnar replies asking what Ecbert would be willing to pay. In Hedeby, Lagertha is now remarried to an abusive husband, Earl Sigvard, and both she and Bjorn are unhappy. Meanwhile, Aslaug gives birth to a son with a serpent in his eye, thereby proving that she is a Völva. Bjorn wants to go out into the world and prove
Ragnar meets King Ecbert, who questions his reasons for staying in Wessex and offers to grant him some land. Later, back at camp, one of Horik's ships arrives with news of Jarl Borg's sacking of Kattegat. Ragnar and his men set sail for home. Athelstan chooses to remain with Horik, but is later captured by soldiers after his hunting party is ambushed. Rollo hides Aslaug, Siggy and the other survivors at a remote homestead and tries to rally others to help them retake Kattegat. Ragnar returns hom
Concerned that Borg is heavily entrenched, Ragnar plans to lure him away from Kattegat. Ragnar and Bjorn sneak into the town at night and set fire to the winter food stores, forcing Borg to give chase. Ragnar engages Borg's forces in a bloody battle, and Borg's host is routed and forced to flee. Ragnar reenters Kattegat, and Bjorn is asked to sacrifice a prisoner to the gods. Aslaug tells Ragnar she is pregnant again but is afraid how the prophecy will impact their child. Ragnar visits the Seer
King Horik returns to Kattegat, defeated by King Ecbert and with few of his forces surviving. Hungry for revenge, Horik tells Ragnar that they need the help of Jarl Borg again, since he has many ships. Aslaug is not pleased and asks Ragnar not to listen to Horik. Rollo is sent as emissary to Götaland to negotiate with Jarl Borg, the latter accepts the offer after consulting with the skull of his first wife. Athelstan becomes a confidant of King Ecbert, entrusted to look after secret Roman scroll
Horik and Ragnar agree that they need more ships and warriors to return to England. Horik persuades Ragnar to delay killing Jarl Borg, in case his execution scares off potential allies. Helga reveals that she is carrying Floki's child and they agree to wed. When Helga seeks Ragnar's blessing, Floki claims they do not need it. They instead marry with King Horik's blessing. Ragnar visits the Seer who reveals that Athelstan is alive but spiritually torn. In England, King Ecbert proposes an alliance
Aslaug's prophecy comes to pass when she gives birth to a son with malformed legs. Despite Ragnar's insistence that he should have no future in Viking society and must die, Aslaug keeps him. Ragnar names him Ivar the Boneless. Lagertha arrives in Kattegat with her ships and warriors. In Wessex, Ecbert receives Princess Kwenthrith of Mercia, who is in civil war with her family after murdering her brother. Kwenthrith takes a sexual interest in the Northmen and Athelstan. Sensing Floki's growing ri
While reviewing old Roman texts with Athelstan, Ecbert sees a way to defeat the Vikings. Horik advances towards what he thinks is the Wessex army, but Ecbert catches the Vikings between two troops of cavalry and defeats them. Rollo is badly injured, but is recognised by Athelstan and taken back to Winchester. Ragnar names his son Björn Ironside, as he is unscathed. Ælla wants to destroy the remaining Vikings but instead Ecbert decides to offer them land and to employ them as mercenaries to fight
Horik's wife and children arrive in Kattegat and the village celebrates. To prove to Horik he is trustworthy, Floki poisons Torstein. Horik reveals his plan to kill Ragnar and his entire family. In return for a promise to marry her, Horik orders Siggy to kill Ragnar's children. Þorunn finally gets into a relationship with Bjorn, as a free woman. Athelstan teaches Ragnar the Lord's Prayer. With reinforcements, Horik attacks Kattegat. Arriving in the main hall, he discovers Torstein alive, and see