Ragnar and King Horik return to Kattegat; Ragnar places his trust in those who have stood by him.

With one last chance to take Paris, Ragnar, and his Vikings troops take a daring chance. Ragnar asks Bjorn for a favor that could change the course of Viking history.

Ragnar's plan comes to fruition. The Viking army lands on the coast of Northumbria.

A ferocious battle between the Vikings and the French eventually comes down to Ragnar against Rollo. The outcome will seal the fate of the two brothers.

The Viking army causes panic in the English countryside as King Ecbert and Aethelwulf plan the defense of the realm.

The Viking army sets out and Paris goes into lockdown as the army prepares the defense.

Ragnar's fate is decided.

In Iceland, Ubbe learns the truth about Kjetill and has a difficult decision to make. Back in Norway, the battle against the Rus has had grave consequences. But re-enforcements have arrived, and Bjorn has an idea that may yet save the day.

A new battle for Kattegat is on and only the gods know who will emerge victorious.

Prince Aethelwulf finds himself subject to the Vikings' battle master plan. Ecbert remains behind with a plan of his own.

Ragnar's warriors march on to King Ecbert's villa and are met with a surprisingly vicious welcome party.

King Horik returns to Kattegat with a surprising proposition for Ragnar; Lagertha runs into a less than enthusiastic homecoming from her new husband; Athelstan becomes confidant to King Ecbert.

Three Viking ships sail toward the Royal Villa of King Aelle in eastern England. Ragnar wants ransom in exchange for peace, but the king has a very different plan in mind.

Paris is hit with a second assault. Emperor Charles needs to make a difficult decision.

Ragnar and Ecbert come face to face; Jarl Borg rules Kattegat with an iron fist; Rollo must now become the leader his people need in Ragnar's absence.

Ragnar and Lagertha's fleets depart Kattegat once more for Wessex and this time they bring a group to colonize there. King Ecbert hosts the Norsemen and proposes a deal. Despite the misgivings of some of the other leaders, Ragnar leads his forces into battle once more, but this time as allies of Wessex.

Ragnar and King Horik clash over how to dispense justice to Jarl Borg. In Wessex, King Aelle arrives and Ecbert has an eye on a new alliance.

Bjorn's fleet sails onward and launches a surprise attack. Back in Kattegat, Lagertha continues in her quest for power.

Preparations for the Paris raid pick up speed, and Rollo thinks about the Seer's prophecy.

The battle for Kattegat begins and, as the two armies line up to fight, the Great Heathen Army must decide between a final plea for peace or all-out war. Floki faces discord among the settlers.

Lagertha and Ragnar unite to try to win Kattegat back from Jarl Borg; Aslaug must face the truth of her prophecies; Athelstan struggles to define his faith; Bjorn must once again make a choice.

Ubbe and the settlers open relations with the indigenous people of the new land. Ivar's strategy lures Alfred's forces into a devastating battle.

Ragnar's faith is tested.

Bjorn returns to Kattegat. Harald gains a measure of revenge on Olaf. In Kiev, interesting news reaches Ivar and Igor about Prince Dir.

King Ecbert finds himself facing an entirely new kind of foe; Ragnar races to dominate in the west; Jarl Borg has his own plans in store for the future of Kattegat.

A dangerously ill Ragnar returns to Kattegat, where his suspected death kicks off a scramble to succeed him. Meanwhile, Lagertha engages in a power struggle with her calculating, former second in command, Kalf. Rollo betrays his heritage and remains in Frankia. Floki pays the price for his brutality against the Christian priest.

The battle begins between Ragnar and King Horik's forces against Jarl Borg; Princess Aslaug makes her way to Kattegat.

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.

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.

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.

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.

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.

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?

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Ubbe is forced into hand-to-hand combat. Floki reaches new depths and is met by a shocking sight. Bjorn sets off for Scandinavia with an old rival.

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.

The journey west begins as Ragnar gathers a crew willing to risk their lives to travel into the unknown. Earl Haraldson's paranoia reaches new heights as his fear of Ragnar's success grows.

Lagertha is betrayed, and Bjorn must find a way to support the distraught queen. Floki and his settlers arrive in a new land, but it is far from what they expected.

Bjorn achieves one of Ragnar's dreams. Ivar hatches a new plan while preparing for a divine arrival. In Iceland, a settler returns in a terrible state. King Alfred faces his greatest threat yet.

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.