Lords of the North — Bernard Cornwell

The year is 878. Uhtred, the dispossessed son of a Northumbrian lord, has helped the Saxons of Wessex defeat the invading Danes. Now, finally free of his allegiance to the victorious, ungrateful King Alfred, he is heading home to rescue his stepsister, a prisoner of Kjartan the Cruel in the formidable Danish stronghold of Dunholm. Uhtred's best hope is his sword, Serpent-Breath, for his only allies are Hild, a West Saxon nun fleeing her calling, and Guthred, a slave who believes himself king. Rebellion, chaos, fear, and betrayal await them in the north, forcing Uhtred to turn once more, reluctantly, to the liege he formerly served in battle and blood: Alfred the Great.