804, Thuringia. An orphan boy, called Bengel, lives in a monastery and is teased by the nuns because of his ugliness. He nurses a black rider, who is shunned by everyone and is said to have the plague, back to health. The rider tells him about the missing Bogumil, son of the Slavic king Slavomir, who was to marry Reglindis, the daughter of the Margrave of Thuringia, by order of Charlemagne. And he asks Bengel about his origins. Bengel now believes he is Bogumil. He goes to the castle and meets a beautiful girl who also thinks he is beautiful. It is Reglindis, she is blind. The girl senses the boy's inner beauty and is very fond of him. Her father, however, wants to kill him. Bengel narrowly escapes death twice, the Black Rider impressively proves his identity with Bogumil and finally there is a happy ending.