The setting is late medieval but not precisely historical, as the hero is "Roland, only son of the emperor" and as far as I know there was no such person. During a period when robber barons are making trade along the Rhine impossible, Roland, who has been incognito as a young sword maker, offers to lead 20 young craftsmen he has trained in swordsmanship in fighting their way down the Rhine from Frankfort to Cologne escorting a barge full of merchandise. ( )