Season synopsis
Contains spoilers for this season and earlier seasons.
Ragnar Lothbrok is a farmer who believes the Norse can sail west to richer lands beyond the familiar Baltic routes. Earl Haraldson forbids the voyage, so Ragnar and shipbuilder Floki secretly finish a longship and recruit a small crew. They reach Lindisfarne, raid its monastery and return with treasure and the monk Athelstan, whom Ragnar keeps alive. Haraldson claims most of the plunder, but the journey proves Ragnar’s route is possible and makes him a threat to the earl’s authority.
A second Northumbria raid turns deadly when Knut attacks Lagertha and she kills him. Haraldson uses the killing to prosecute Ragnar, then attacks his farm and captures Rollo. Ragnar challenges the earl to single combat, kills him and becomes Earl of Kattegat. He leads another voyage to England, where the Vikings defeat King Aelle’s forces and secure ransom after the king’s first attempt to break the agreement fails. In Ragnar’s absence Lagertha rules but suffers a miscarriage; the family also loses Gyda to plague.
At Uppsala, Ragnar pledges himself to King Horik, who sends him to negotiate with Jarl Borg over contested territory. The mission fails when Horik rejects compromise, and Rollo—jealous of Ragnar’s rise—agrees to support Borg. The plague also kills Siggy’s daughter Thyri. Meanwhile Ragnar meets Princess Aslaug during the journey and sleeps with her; she later tells him she is carrying his child. The season ends with Ragnar’s household still in Kattegat and the rupture between Ragnar, Rollo and Borg poised to become a new conflict.