Season 4 follows Ragnar Lothbrok as his power and ambitions continue to grow. After returning from Paris, Ragnar faces serious problems within his family and among his fellow Vikings. His relationship with Floki, Lagertha, and his sons becomes increasingly complicated. Ragnar eventually returns to Paris, where the Vikings launch another major attack. Meanwhile, his sons begin to grow into strong warriors and start creating their own reputations. The season also focuses heavily on Ragnar's struggles, betrayals, family conflicts, and battles. Later, Ragnar's actions lead to major changes in Kattegat and set the stage for his sons to become important characters in the Viking world.