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. Meanwhile, Floki faces discord among the settlers.
Guided by Bishop Heahmund's visions, the Saxons devise a battle plan. Meanwhile, Ivar the Boneless strategizes on his own as the Vikings face increasing pressure; and Bjorn Ironside finds himself in a new territory and must convince the local commander he is a trader and not a raider.
Conclusion. As the Vikings establish their stronghold in York, Ivar is determined to lead the Great Army. Meanwhile, in Kattegat, Lagertha misjudges King Harald and pays a heavy price; and Floki arrives in a mysterious land.
Part 1 of 2. Tensions mount between the sons of Ragnar Lothbrok as the Vikings continue to threaten the very heart of England. As the army moves to take York, with King Aethelwulf and his family still in hiding, Heahmund, the warrior bishop, must rally the Saxons to defend the realm.