Six months after the battle of Kattegat and Bjorn is now the king. As he struggles with the responsibilities of kingship, he finds he can't rely on his mother, who has other plans. Ivar falls into the hands of Kievan Rus and may have finally met his match. Intrigued by Ivar's claim to be a god, Oleg decides to put him through a test.
Messengers arrive in Kattegat with news that present Bjorn with a dilemma. As Bjorn tries to do the right thing, Prince Oleg of Kiev seems untroubled by his conscience. Lagertha settles into her new peaceful life, but danger is nearby.
Lagertha is visited by women from nearby villages and they feast together happily, however the community is shattered by shocking events. In Kiev, Oleg continues to be friendly to Ivar who is aware of the threat he poses not only to himself, but also to the young heir of the throne. Bjorn has answered the call and comes to the aid of an old enemy, but all is not right as disaster looms for his forces.
Lagertha leads her village's response to the recent attacks, but when the attack comes the consequences are tragic. Olaf has a bold new plan for the future Norway. In Kiev, although Ivar discusses Oleg's ambitions for Scandinavia, he's more interested in the plight of Igor, the young heir who Oleg controls.
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.
Bjorn is forced to act quickly in the aftermath of the election for the king of all Norway. The Bandits attack Lagertha's village again confident of an easy victory. However, when the defense boils down to single combat with Lagertha, victory seems less likely. In Kattegat, haunted and paranoid, Hvitserk continues to unravel.
Bjorn returns to Kattegat. Harald gains a measure of revenge on Olaf. In Kiev, interesting news reaches Ivar and Igor about Prince Dir.
Bjorn faces a difficult decision. In search of new lands and old friends, Ubbe and Torvi leave Kattegat. Oleg's plans for the invasion of Scandinavia are taking shape. King Harald is baffled by the origin of a mysterious raiding party.
Ubbe and Torvi meet a mysterious wanderer in Iceland. Bjorn is forced to reconsider who his enemies are when Erik returns from a scouting mission with some worrying information. Bjorn will need allies, but can he convince his old foe, King Harald, to join forces in the face if a new threat? Ivar is reunited with someone close to him.
Ivar and Igor may be plotting against Oleg, but they're still part of the force that will depart Kiev to invade Scandinavia. King Harald and King Bjorn begin preparations for the invasion. But can enough be done to resist the Rus force?
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.
The mood has changed when the Rus army returns to Kiev and Oleg isolates Ivar. But Dir confirms that he's mustering a force to overthrow Oleg and Ivar is part of the plan. Ubbe and a group of settlers depart Iceland, in search of the Golden Land.
It's Election Day in Kattegat and all eyes are on the voting, but strangers arriving at the harbor may force a very unexpected outcome. Ivar receives the signal from Prince Dir that his forces are ready to challenge Oleg.
Prince Igor receives a hero's welcome in Novgorod but back in Kiev the mood is darker: Prince Oleg will not be giving up the fight. Meanwhile, Ubbe's settlers are overjoyed to find land, but it's not the Golden Land they expected.
A fight erupts in Greenland and Ubbe, Torvi and Othere barely escape with their lives... in a leaking boat with no supplies. And in Kattegat, Gunnhild makes a bold move.
Out in the open sea, Ubbe and the settlers are at the mercy of the elements. Tension mounts between Ubbe and Othere and when baby Ragnar begins to weaken, it's the final straw for Ubbe. Meanwhile, Ivar and Hvitserk return to Kattegat.
When King Alfred of Wessex hears about the arrival of the sons of Ragnar, with an army, he knows he must take drastic action. So as the Viking army makes camp and lies in wait, Alfred and his army abandon the Royal Villa and march to meet them.
Ubbe and the settlers find land, but soon realize they're not alone. In Wessex, King Alfred has mustered a large force to meet the Vikings. Meanwhile, in Kattegat, Erik realizes that Ingrid has been using her powers against him.
In the new land, Ubbe and the settlers engage in careful diplomacy when they are surrounded by the locals. In Wessex, the Vikings ambush the Saxon army, but Alfred is convinced the Lord is with his army and refuses to retreat.
The epic saga which began with Ragnar Lothbrok, the first Viking hero to emerge from the mists of myth and legend, comes to an end in a spectacular and shocking series finale which finds tragedy striking in the new land and in England.