As Norway’s Kings and Jarls arrive at Harald’s territory for the election of the King of all Norway, Olaf is certain of the result, however, it may not go as smoothly as he believes. Lagertha’s village is anxious in anticipation of another attack and she is relieved when Gunnhild arrives with re-enforcements. In Kiev, Igor and Ivar engage in subterfuge and Ivar is stunned when he encounters a ghost from his past.

An unexpected turn amongst the settlers leaves Floki powerless. King Alfred confronts Judith. In York, Bjorn must strike a deal with Harald. Wessex is once again threatened by a Viking force, but who will lead the Saxon army to defend the Realm?

As his enemies scheme for power, Harald prepares for his coronation and chooses a queen. Ubbe's party reaches shore — but not the one they're seeking.

Heahmund must try to convince King Alfred that his actions are in defense of the Crown. Ubbe and Torvi strengthen the position of the Vikings but not all in the Viking camp support their strategy. Another settler disappears in Iceland.

As the celebrations for Ivar continue in Kattegat, grief hits Iceland and Floki must now make a fated decision. Harald's army approaches Wessex. A conspiracy grows against King Alfred.

Ubbe persuades the settlers in Iceland to embark on a voyage of exploration. The defeat of the Rus creates power vacuums in both Kattegat and Kiev.

Ubbe and his followers languish on the open sea. Ivar and Hvitserk receive a frosty reception in Kattegat, until a restless Ivar has a revelation.

In Iceland, Ubbe and Torvi finally meet a mysterious wanderer. Bjorn is forced to re-think who his enemies are when Erik returns from a scouting mission with worrying information. Bjorn will need allies, but he may not be able to convince his old foe, King Harald, to join forces in the face of the new threat. Ivar is reunited with someone close to him.

The election for Kattegat's new ruler is held, but a surprise visitor disrupts the proceedings. Ivar puts his plan to overthrow Oleg into action.

A sense of doom looms over Kattegat as bloodshed ensues. The defeated army flees in the face of the victors. A legendary warrior makes his way home.

Lagertha is forced to take action. In Kiev, although Oleg continues to be friendly, Ivar is aware of the threat which Oleg poses to the vulnerable young heir to the throne. Bjorn has answered the call and come to the aid of an old enemy.

Factions in Greenland spill blood, driving Ubbe's company away. Troops under Ivar and Dir seize Kiev for Prince Igor. Gunnhild makes a fateful choice.

Ivar and Hvitserk lead King Harald's army to England, where King Alfred of Wessex abandons his royal villa and marches to meet the sons of Ragnar.

The army leaders consider their options in the aftermath of the battle. In Floki's camp, all hopes of binding the community together are dashed as tragedy unfolds.

It’s six months after the battle of Kattegat and Bjorn is now King. As he struggles with the responsibilities of kingship, he finds he can’t rely on his mother. Ivar falls into the hands of the Kievan Rus, and in their ruthless and unpredictable ruler, Prince Oleg, he may finally have met his match.

Messengers arrive in Kattegat with news that presents Bjorn with a dilemma. Prince Oleg of Kiev seems untroubled by his conscience. Lagertha has settled into her new, peaceful life, but danger lurks nearby.

Lagertha leads her village's response to the recent attacks, but despite her best efforts, the consequences are tragic. Olaf has a bold new plan for the future of Norway. Ivar discusses Oleg's ambitions for Scandinavia.

Bjorn returns to Kattegat to learn that an attack will take place during the next full moon. Ivar must decide if he can place his trust in a former enemy on the battlefield.

Ivar is crowned the new king of Kattegat just in time to welcome Rollo home. Bjorn, Lagertha and Ubbe must rely on unsteady alliances to survive.

Hvitserk is severely tested. Floki makes an amazing discovery. Freydis gives Ivar a surprise. Ubbe negotiates with the three Danish Kings that have massed their armies in Reading, but the negotiations may have a perilous outcome.

Bjorn faces a difficult decision. Ubbe and Torvi leave Kattegat in search of new lands and perhaps old friends. Oleg's plans for the invasion of Scandinavia take shape. King Harald is baffled by the origin of a mysterious raiding party.

King Alfred falls ill as the Viking army seizes the high ground. Ingrid curses Erik. Ubbe and his people find a new world — but they're not alone.

Farmer, family man and rebel Ragnar Lothbrok is determined to sail west to discover new lands and riches despite an intimidating warning from his village's tyrannical leader, Lord Haraldson, who makes it clear in no uncertain terms that doing so could result in severe consequences.

The traditional pilgrimage to Uppsala to thank the gods brings a torrent of emotions for Ragnar, Lagertha, and Athelstan. Ragnar, pulling farther away from his wife goes to make peace with the death of his unborn son. Lagertha, still reeling from her miscarriage, wants to find out from the gods if more sons are in her future. As the Vikings come together to sacrifice and give thanks to their gods, Athelstan discovers just how strong his Christian faith still is.

Bjorn, Lagertha and Ubbe face an uncertain fate as Heahmund's loyalty is tested. Floki fights to understand the will of the gods. Ivar may have met his match.