In December 1943 the Germans attack a partisan camp in the Abruzzo mountains behind Cassino. One man, a British prisoner-of-war, escapes. Robert Johnson can only survive by becoming Roberto DiGiovanni, an Italian peasant who can move freely in the snowbound mountains and German-garrisoned villages, protected by the communist underground. Together they have to endure manhunts, informers, political manoeuvring between communists and fascists, bombing raids and growing famine. It is not only Robert who has to change: the families, communist and fascist, who protect him, the daughter of the fascist family who falls in love with him, the doctor, the priest and the peasants with whom he reforms the partisan band all have to adapt their loyalties in order to survive.