1010 AD: England is dying, its people brutalised and its lands ravaged by wave after wave of Norse invaders. King thelred does little but sit on his throne, haunted by his own troubled past and incapable of action. When the infamous "jomsviking", Thorkell the Tall, lands on his shores with an unprecedentedly vast horde, thelred predictably struggles to find a solution, preferring instead to fixate on supposed slights and schemes set in motion by his manipulative advisers.
As his kingdom reels under Thorkell's assault, thelred only becomes more unstable, finding his nights plagued by dreams of his murdered half-brother, the martyred King Edward, and those he believes hold him responsible for his death. Seeing enemies everywhere, thelred lurches from calamity to calamity, compelling his sons, the noble thelstan and Edmund, to act against him for the good of the realm.
Unbeknownst to the two brothers, their father's dreams are far more than they appear, holding the secret to his own salvation and a part yet to be played by a mysterious hero who is himself unaware of his role in what's to come.