Alastair Macleod 
Ulla Flota á Fæti, 
or The Flight Over the Flow Country

Ulla Flota á Fæti: Ulla, Fleet of Foot, the fourteen year old daughter of Helga Svan Hud and Harald Svartur Skegg, suddenly finds her peaceful life changed for ever when a blood feud from the past comes back to haunt her parents.

It is 1014 and some of the Vikings, in the fleet bound from Orkney to Ireland for the great battle of Clontarf, take a detour to deprive a woman of her rightful inheritance.