The eponymous "Quintus" (Michael Fassbender) is struggling through the snow to escape the menacing Picts who have just ambushed and destroyed his outpost. He has to get the message to "Gen. Virilus" (Dominic West) before the whole of Britain is overrun by these warlike people. That man commands the ninth legion, and en masse they head north into the perilous wilderness - guided by "Etain" (Olga Kurylenko) - to seek vengeance. Further into enemy territory they go before betrayal and disaster befalls them. Only "Quintus" and a few of his colleagues manage to escape. Can they make it to Hadrian's...