Season 3 follows Ragnar as he becomes more powerful and continues his ambitions in England and France. He returns to Wessex with his Viking army, but tensions grow between the Vikings and King Ecbert. Ragnar also leads his warriors on a dangerous expedition to Paris, where they face strong defenses and a powerful enemy. Meanwhile, Lagertha struggles with her own political problems, and Floki becomes increasingly suspicious of Ragnar’s relationship with Christianity. The season is filled with war, betrayal, power struggles, and Ragnar’s ambition, ending with a major turning point for the Vikings.