Season three culminated with the extraordinary battle in Paris, where Ragnar seized victory from the jaws of defeat – but still returns to Kattegat dangerously ill. Thoughts of his death galvanize the forces who seek to succeed him as king, including his wife Ragnar’s reappearance in Kattegat triggers a chain of events no one – except the Seer – could have ever imagined. He unexpectedly arrives home to see what has become of his sons and to handle unfinished business in Wessex with King Ecbert (Linus Roache). Meanwhile, Lagertha (Katheryn Winnick) plans a power play in Kattegat and Bjorn (Alexander Ludwig) prepares to fulfill his long-held dream to explore the Mediterranean in a sleek new boat built for him by Floki (Gustaf Skarsgård).