A sense of doom looms over Kattegat as bloodshed ensues. The defeated army flees in the face of the victors, and a legendary warrior makes his way home.
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 battle for Kattegat begins and the Great Heathen Army must decide between a final plea for peace or all-out war. Floki faces discord among the settlers.
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.
Ivar meets his match in Bishop Heahmund; Floki returns to Kattegat; Bjorn receives a lavish welcome in North Africa.
Guided by Bishop Heahmund's visions, the Saxons devise a battle plan. Ivar the Boneless strategizes on his own as the Vikings undergo increasing pressure. Bjorn Ironside finds himself in a new territory and must convince the local commander he is a trader and not a raider.
Celebrations are cut short in the aftermath of the battle at York; Ragnar Lothbrok's sons are pitted against each other as tensions reach an all-time high, and each one is forced to choose a side.
Tensions mount between the sons of Ragnar Lothbrok as the Vikings continue to threaten the very heart of England.