Thueringen, 804 A.D. An orphan boy named Bengel lives in an abbey, teased by the nuns because of his ugliness. He nurtures the Black Knight back to health, though he's thought to have the Plague, so everyone else shuns him. The Knight tells Bengel about the missing Bogumil, son of Slav king Slavomir, who on Charlemagne's order was to marry the Thueringian Margrave's daughter Reglindis. He also asks Bengel about his ancestry. Bengel now believes that he is Bogumil. He goes to the castle, where he meets a beautiful girl who thinks he's just as handsome. It is Reglindis, and she is blind. She finds his inner beauty and devotes herself to him, but her father wants to get rid of him. Bengel barely escapes death twice, the Black Knight reveals his identity with a flourish to Bogumil, and everyone lives happily ever after.