AD 117. The Roman Empire stretches from Egypt to Spain, and East as far as the Black Sea. But in northern Britain, the relentless onslaught of conquest has ground to a halt in face of the guerrilla tactics of an elusive enemy: the savage and terrifying Picts. Quintus Dias (Fassbender), sole survivor of a Pictish raid on a Roman frontier fort, marches north with General Virilus’ (West) legendary Ninth Legion, under orders to wipe the Picts from the face of the earth. However, when the legion is ambushed and Virilus is taken captive, Quintus faces a desperate struggle to keep his small platoon alive behind enemy lines. Enduring the harsh terrain and evading their remorseless Pict pursuers, the band of soldiers race to rescue their General and to reach the safety of the Roman frontier.