Arn Magnusson remembers, as a fearful crusading templar, his youth in fractured Sweden's West Gotland. He and his brother Erskin were friends with king Erik's son Knut, until a neighboring warlord killed the king to seize the crown during the local church's solemn consecration. After Arn's seemingly fatal fall and 'miraculous survival', his mother insisted on keeping a promise to God to offer the boy as oblate to the regional abbey. There abbot Henri allowed father Guilbert, a former templar, to add warrior skills to his monastic education. After an incident in which he was forced to kill a bride-robber in a duel, Arn tries to prevent his family's feud with a haughty neighbor's getting bloodily out of hand.