Guided by Bishop Heahmund's visions, the Saxons devise a battle plan; Ivar the Boneless strategizes as the Vikings undergo increasing pressure; Bjorn Ironside finds himself in a new territory and must convince the local commander he is a trader.
Bjorn and Halfdan are at the Pillars of Hercules, the entrance to the Mediterranean sea. Bjorn tells them that he wants to go to Rome but Sinric tells him that the Roman empire is no more. Bjorn says then if not Rome then where shall they go. Sinric tells them to go to an island called Sicily. Outside of York, Aethelwulf tells Heahmund that they must return to Essex and recruit another army. Heahmund disagrees and tells Aethelwulf that he had a vision. Alfred tells him he speaks in riddles. Heahmund tells them that what he saw were dead bodies lining the streets of York because they ran out of food to eat. Heahmund tells them to prevent the Northman from coming and going and trap them in York. Aethelwulf agrees to this plan. Ubbe returns to Kattegat. Lagertha thanks him for getting revenge on Ragnar's death. Ubbe tells them that Bjorn is a good man but that Ivar is a different story. Ubbe says that he is now at war with Ivar and that Hvitserk is now his enemy as well since he sided with Ivar. Lagertha tells him that she'll support him against Ivar if he supports her against King Harald. They clink glasses in agreement.
Torvi tells Lagertha to not trust Ubbe too much because Bjorn is supposed to rule Kattegat after Lagertha. After having sex, Margrethe tells Ubbe that Lagertha is losing her power and that Ubbe should take her place of ruling Kattegat. Bjorn arrives in Sicily. While out gathering food, the Northmen are attacked by Alfred and the people in York are denied food once again. Hvitserk tells Ivar about the hunting party not returning. Ivar makes fun of Hvitserk for being Ubbe's dog. Hvitserk gets upset and leaves. Margrethe talks to Torvi about Lagertha but Lagertha overhears them talking. Lagertha tells Margrethe that she can conspire against her or she can choose to be loyal to her now that she's a free woman. Margrethe starts to cry and leaves. Northumbrians arrive at Aethelwulf's camp. Judith's cousin Mannel greets them and swears his loyalty to King Aethelwulf. Bjorn arrives to the city of Sicily and is introduced to Euphemius. They tell him that they are traders but Euphemius attacks them. Bjorn manages to disarm Euphemius and points his own blade at him. Euphemius welcomes them to his city.
Bjorn learns that they aren't the first Northmen to come this way. Commander Euphemius wants Bjorn and his men to be his bodyguards. Bjorn agrees. Lagertha goes to see the Seer and asks if she'll see Bjorn again. He says yes but only in terrible circumstances. He tells her to prepare herself for what is to come. Hvitserk asks Odin if he made the right choice to side with Ivar and asks what his fate is. Suddenly, they are attacked by arrows. Sinric tells Bjorn that Commander Euphemius isn't really the commander here after all. That he has no real power but that a man called Ziyadat Allah rules from Africa. Bjorn says that he wants to meet Ziyadat Allah since it seems like he is the true leader. Heahmund says that his vision has come true but that they should wait to attack. This upsets Aethelwulf because he feels like Heahmund puts himself before him despite Aethelwulf being king. Aethelwulf tells him that they will proceed together but only for the sake of England.
Hvitserk asks Ivar why he's pretending to burn their dead. Ivar says that he has a plan against the Saxons. Hvitserk asks what the plan is but Ivar tells him that he'll know in due time. Floki decides to head back to civilization and invite other men and women to live with him in this new place that he's found. Astrid approaches Harald. She tells him that she's made up her mind. She agrees to marry him. They are married shortly after. Bjorn asks Euphemius to meet Ziyadat Allah and invites Euphemius to come with them. At first Euphemius says no but then agrees when Kassia threatens to leave him. Halfdan wonders who Kassia is since she holds so much power over Euphemius. A rider arrives and tells Aethelwulf that the Northman have gone. They go to York and investigate. All they find is some horses and rats in the chapel. Heahmund asks why the rats are above ground.
- Katheryn Winnick as Queen Lagertha
- Gustaf Skarsgård as Floki
- Alexander Ludwig as Bjorn
- John Kavanagh as The Seer
- Peter Franzén as King Harald 'Finehair'
- Jasper Pääkkönen as Halfdan the Black
- Moe Dunford as Aethelwulf
- Alex Høgh as Ivar the Boneless
- Marco Ilsø as Hvitserk
- Jordan Patrick Smith as Ubbe
- Jonathan Rhys Meyers as Bishop Heahmund
- Josefin Asplund as Astrid
- Ida Marie Nielsen as Margrethe
- Ferdia Walsh-Peelo as Alfred the Great
- Georgia Hirst as Torvi
- Jennie Jacques as Queen Judith
- Albano Jerónimo as Euphemius
- Karima McAdams as Kassia
- Frankie McCafferty as Sinric
Additional Cast (in order of appearance)
- Darren Cahill as Aethelred
- Jonathan Delaney Tynan as Lord Cuthred
- Ben Roe as Guthrum
- Paul Reid as Mannel
- Aoife Maloney as Chief Priestess
- Viking Hunting Party
- Halfdan's runic inscriptions are a reference to the runic inscriptions in the Hagia Sophia, which bear the name "Halvdan." These inscriptions were carved in the 9th century.
- Katheryn Winnick and John Kavanaugh are both missing from the opening credits in the American broadcast due to an error.