In the show's second season, Nordic warrior hero Ragnar Lothbrok is plunged into a bloody quarrel between the Viking nation's two most powerful men. Later, Princess Aslaug arrives in Kattegat and springs a surprise that puts Ragnar in a quandary.

With his taste for conquest undimmed, Ragnar decides to lead his band of warriors against Paris -- despite the city's imposing fortifications and the fearsome presence of Roman legions.

After his stunning battle in Paris, Ragnar returns to Kattegat near death. News of his fragile condition begins to inspire covert maneuvers among those who would succeed him, including Queen Aslaug and Ragnar's son, Bjorn.

After being vanquished in battle by his brother and then vanishing for six years, Ragnar finds Kattegat vastly changed upon his return. Meanwhile, he has some unfinished business with the duplicitous King Ecbert.

When Ivar the Boneless gains control of the Great Heathen Army and kills his brother, Sigurd, war with Ragnar's sons is inevitable after they take revenge for their father's death. Later, Bjorn again sets out to sea.

Ivar the Boneless' tyrannical reign as king of Kattegat ushers in a new Dark Age for Scandinavia. And while Bjorn and Lagertha flee Ivar's murderous forces with Bishop Heahmund, Duke Rol lo's return brings even more upheaval. Meanwhile, Floki battles the elements-as well as his settlers' lust for revenge-in beautiful, desolate Iceland. Ultimately, the sons of Ragnar and old sworn enemies must become allies to challenge the despot Ivar, who has declared himself a god.

Six months have passed since the battle of Kattegat, and Bjorn has stepped into the role of king but struggles with the responsibilities. Later, messengers arrive with news that leaves Bjorn facing a dilemma.

As we approach the end of our epic saga, the tumultuous conflict between the Rus and the Vikings comes to a conclusion, with grave consequences. While in Iceland, Ubbe is determined to fulfill his father Ragnar's dream and sail farther west than any Viking has traveled before. And there is unfinished business in England. The Vikings have established settlements there and overrun most of the country - except for Wessex. The King of Wesex, Alfred the Great, is the only Sussex ruler to seriously challenge their complete domination. Ivar the Boneless must again face, in battle, the king he only knew as a boy for a final reckoning.