Sword of Kings is set in 10th-century England and continues to follow the fortunes of the fictional Uhtred of Bebbanburg.

He learns that Ealdorman Æthelhelm ordered Waormund, a huge, sadistic warrior and one of his most trusted men, to try to kill Uhtred.

Edward's will gives the kingdoms of Wessex and East Anglia to Ælfweard and Mercia to Æthelstan; Uhtred realises that this will inevitably result in civil war.

Uhtred becomes concerned when he discovers that Merewalh, the commander of the garrison, has taken most of his men and marched east, having been deceived into believing that an enemy army is approaching.

Uhtred persuades Merewalh to give him 180 of his warriors and to agree to his plan to attack Lundene, despite being seriously outnumbered.

A sizeable part of Æthelhelm's forces are from East Anglia and have no real stomach for battle; as Uhtred had hoped, they stay out of the fighting.

Kirkus Reviews said the Sword of Kings "is historical adventure on a grand scale" and compared it to "the works of Conn Iggulden and Minette Walters", highlighting how "Cornwell paints vivid images of the filth in the Temes and in cities like Lundene".

They noted that "few women are active characters", though "the action is believable if often gruesome and loathsome, and it never lets up for long".