When safely back at Kattegat with King Horik, Ragnar only trusts those who stood by him.
Ragnar's invading party are met with extreme violence when they march on King Ecbert's villa.
Horik and Ragnar travel to Wessex, but their true purpose is disputed. Meanwhile, Princess Aslaug's prepares to give birth.
Justice is dealt to Jarl Borg, and allies are made on both sides of the sea.
Ragnar receives an unexpected offer from King Horik and Lagertha's new husband doesn't seem overly pleased to see her. Meanwhile, Athelstan becomes King Ecbert's trusted aide.
Lagertha is once again reunited with Ragnar and Bjorn make another choice. Meanwhile, Athelstan finds it difficult to define his faith and Aslaug has to accept the consequences of her prophecies.
While Ragnar meets Ecbert in search of a compromise, Rollo must lead his people. Meanwhile, Jarl Borg imposes a strict rule on Kattegat.
While the raids on Wessex continue, Ragnar attempts to rule in the west. Meanwhile, King Ecbert faces a new kind of enemy and Jarl Borg makes his own plans for Kattegat.
Four years have passed and Ragnar leads a new series of raids on England.
As Princess Aslaug journeys to Kattegat, Ragnar allies himself with King Horik in the battle with Jarl Borg.