Years have passed since the events of the last season, and King Edward is still forging ahead with his ambitions to unite the Saxon Kingdoms to fulfil his late father's dream. Although a long-standing peace between Danes and Saxons now exists, that harmony is under threat. Not only by a new Danish invasion but a Saxon rebellion. Uhtred has been entrusted with protecting Edward's illegitimate son, the future King of England, Aethelstan. But the treacherous Lord Aethelhelm has ambitions for his grandson Aelfweard, Edward's other son, to rule. We follow Uhtred as he faces his greatest enemies, and suffers immeasurable loss, on his quest towards fulfilling his destiny. Meanwhile, Edward treads a fine line between peace-keeper and authoritarian as he battles to bring together the fractured Kingdoms of the land. In a surprising twist of fate, Uhtred discovers that the quest to unite England may well be linked to his own personal destiny.

Ill omens and border raids make Uhtred extra-vigilant at his northern outpost. King Sigtryggr is visited by his notorious brother Rognvaldr.

A betrayal at Eoferwic sends Sigtryggr in search of aid, while Uhtred begs Aethelflaed for military support she cannot give. Edward meets a new ally.

In the aftermath of the tragic battle for Eoferwic, Sigtryggr is forced to make a painful choice. Edward learns of Aethelhelm's intrigues in Mercia.

Rivals secretly advance competing successors upon the death of a Mercian ruler. Brida finds solace in the faith of her prisoner, Father Pyrlig.

Aethelhelm's subterfuge successfully foments war tensions between Edward and Sigtryggr, but his thugs make a crucial mistake in attacking a pilgrimage.

The forces of Edward and Sigtryggr march toward battle as Uhtred races to reveal the truth of Aethelhelm's scheming and avert a ruinous war.

Edward offers a role to Stiorra that would restore her to power. Aethelhelm meets with a Saxon enemy. Uhtred has a long-overdue reckoning with Brida.

Upon learning of Aethelhelm's location, Uhtred proposes an audacious attack to rescue Aelfwynn and restore his birthright β but Edward is cautious.

Edward marches his troops north while Uhtred recruits a small force to infiltrate Bebbanburg. King Constantin arrives to meet his new bride, Aelfwynn.

Armies converge in an epic, final showdown that determines the fate of a king's dream for England β and Uhtred's hope of securing his family's future.