Immanuel Rath (Emil Jannings) is an esteemed educator at the local Gymnasium – a college preparatory high school – in Weimar Germany. He punishes several of his students for circulating photographs of the beautiful Lola-Lola (Marlene Dietrich), the headliner for the local cabaret, "The Blue Angel". Hoping to catch the boys at the club, Rath goes there later that evening and meets Lola herself.
A young schoolmistress arrives in a small village to teach reading and writing to boys and men. A hooligan sees her on the street and falls in love with her. Soon he begins to attend her classes. When one lesson is disturbed by one of the students, he beats him. The student seeks revenge with the help of his father and some of his friends. The hooligan is stabbed to death in a fight. Before dying, he asks his mother to call the schoolmistress. After the schoolmistress has kissed him on the lips, he closes his eyes and dies.