Plot

It should first be mentioned that there was an English-language version of the film shot simultaneously with the German-language version. Both versions are nearly identical, but there are a few exceptions in the story. Due to the classic nature of the film, this synopsis is based on the original German version of the film.

The film opens with the sound of geese and chickens clucking in a street marketplace. A woman washes a window outside a shop featuring a poster of Lola (Marlene Dietrich) which causes the woman to pose in a similar fashion. A shot of a door which reads "Prof. Rath" introduces the other main character, Professor Immanuel Rath (Emil Jannings) who is preparing for class. A bell is heard ringing in the background as teenage schoolboys run to class. The caretaker of the house is cleaning up the house as she reminds the Professor of breakfast. The Professor enters and has some tea/ coffee and begins to whistle to his bird. When he doesn't hear a reply he checks on the bird only to find it has died. This seems to sadden the professor, which is contrasted by the housekeeper taking the bird and dumping it in an open boiler. All she can say is: "Anyway, he stopped singing long ago." The Professor goes on with his breakfast.

We are then introduced to his class which is mostly composed of boys gathering in a group to look at a postcard, while one boy wipes a blackboard. The boy holding the card is blowing on it to make it react in a particular fashion that will be shown later. One boy sneaks up to the desk and takes the Professor's notebook and alters it to say Prof. Garbage (an easy pun in German, involving the mere addition of an "Un-" to the Professor's surname) and attempts to draw a crude illustration of the Professor until the pencil breaks.

The Professor is then shown leaving his house for class, which is followed by the chiming of a large cuckoo-type clock. The clock is shown along with birds ironically perched on it and its statue figure which passes by from one side of the clock to the other as it chimes. The shenanigans are quickly broken up by a student barking "Watch out! The old man!" The students quickly return to their seats and are just as quickly instructed to sit down. The Professor takes his seat and blows his nose with his handkerchief, which leads to his noticing that his notebook has been defaced. He searches the class for the culprit and homes in on the most nervous of the bunch, Angst (the aptly-named character played by Rolf Muller). He instructs Angst to erase the additions, while Angst attempts to plead his innocence. The professor doesn't care and makes him erase it regardless.

The Professor resumes his lesson for the day leading off with a passage from Hamlet, Act III, Scene 1 (the famous "To be or not to be" soliloquy). The Professor chooses a student to recite some of Hamlet, only to interrupt him because of his poor pronunciation of English. The Professor attempts to get the student to say "the" instead of "za" by placing a pencil in his mouth. He finally gets frustrated and has students write a paper on how the story of Julius Caesar would have differed if Mark Antony had not delivered his eulogy (yet another reference to a tragic and ill-fated Shakespearian character!). One student appears to be cheating, but is actually looking what is revealed to be a Lola postcard with a dress that can be blown to reveal her undergarments. The Professor realizes this and takes the card saying warning his students that there will be consequences as he places it in his own notebook. The troublemakers are not happy about this, while Angst, the teacher's pet, is pleased by the Professor's discovery implicating the other boys. The troublemakers decide to take action against Angst.

After class is out the troublemakers hide outside the door and wait for Angst to leave class. When he does they trip him, causing his books to fly open on the ground. Angst's books have cards with Lola on them, which upsets the Professor. Angst and the Professor go to his office to talk about the cards. Angst swears the cards do not belong to him, but the Professor doesn't care for Angst's protestations, regardless of whether he is innocent or not. Angst then tells the Professor that the others don't like him because he doesn't go out at night to The Blue Angel with them to see girls. The Professors interest is piqued by these new facts.

The Blue Angel is a cabaret featuring women singing more than dancing on a stage. Lola is finally seen on stage for the first time performing. She sings as the Professor is shown entering the bar. Meanwhile the students are backstage with Lola trying to sweet-talk her. Lola flirts, but does little more with the students. She then takes the stage again singing of her longing for a real man, a he-man, which leads to her declaring she will find the one tonight.

This is followed by the Professor's entrance. The students see him enter and run to hide backstage. The Professor looks in the crowd for the students, but is interrupted by Lola's spotlight being pointed at his back. He turns to see Lola in person for the first time as she seems to be singing to him.

This is interrupted when he sees one of his students and begins to chase him. As he looks through the rooms backstage he stumbles upon a very sad clown - an oddly foreboding image. There is a brief scene of a heavier woman doing a dance with only her eyes as a Middle-Eastern type of music is played.

Meanwhile Lola comes backstage and asks what the man is doing in her room. After some pleasantries are exchanged she begins to undress to change into her next costume. The Professor seems very thrown off by this, leading him to block the doorway through which people are moving on and off stage. He is then referred to as a "roadblock" which causes him to move back out of the way. Lola goes upstairs and drops her panties to the Professor, then comes down fully dressed for her next performance.

At this point the loud Magician is introduced, yelling to the other women performers. He is protective of Lola until he learns of the prestige of Dr. Immanuel Rath. Suddenly the Magician Kiepert (Karl Gerron) attempts to relate and justify his job to the Professor. Kiepert then demands that Lola go on stage as he puts on a fake mustache. The Professor accuses the Magician of inappropriately accommodating his students, whereupon the Professor immediately spots one of his students and chases them out.

The next scene is probably the most out of place or random in the movie. Angst is sleeping in his bed when a noise wakes him. Shadows approach as some boys jump out and attack him by slapping him. This is obviously retaliation for telling the Professor about The Blue Angel. The Professor is then shown going home to sleep, but can't seem to shake the memory of Lola out of his head especially because her undergarments have ended up in his jacket mysteriously.

The next day the Professor puts on his coat and goes to return Lola's panties. The Professor arrives, and the students are forced to hide in the cellar. The garments are exchanged, and Lola sees that the Professor is there to see her again. She shows a playful grin as she begins to seduce him, and the students watch from the cellar.

Lola begins her game of cat and mouse. Babying the Professor by combing his hair, then asking him how beautiful he thinks she is. Before things get serious she blows some powder in his face and then treats him like a baby again. Things finally begin to progress with the Magician demanding that Lola drink with a visiting sailor with lots of cash. The sailor treats Lola rudely as the Professor watches. He becomes furious and chases out the sailor after a fight of sorts.

The sailor then returns with the cops, causing the magician to hide the Professor in the cellar. The Professor finds his students and emerges from the cellar, bringing them up with him. The ordeal with the sailor is resolved by the police taking him back to the station because one of the parties to the scuffle is a sober Professor, who is much more credible to the Officer than a drunk sailor. The Professor talks of punishing the students, but only chases them out.

The Professor is then given drinks to calm his nerves, leading to his becoming pleasantly inebriated as he is serenaded by Lola. Lola sings of how she is falling in love again, and can't help it. The song is once again prophetic (like the sad clown and the Shakespearian references) of things to come.

He wakes up in Lola's bed the next morning. Lola has a singing bird which comes as a delight to the Professor. She prepares breakfast for the two of them, which leads to the final part of her plan to trap her new love interest. The Professor runs to school when he hears the school bells. Because he is so late for class, a student is able to draw intricate drawings of the Professor's antics the previous night including one that depicts him as Cupid in love with Lola. The Professor tries to punish the students, but can't keep them under control. The head of the school realises that Rath's authority has been undermined and decides that the his actions have damaged his reputation to the point where he should either resign or be dismissed.

The Professor is left with no choice but to follow his heart and propose to Lola. He packs up his items from the classroom and goes to Lola. One shot of the Professor in the empty classroom shows his despair, as well as being another indication of things to come. The group of travelling artistes Lola is in are packing to leave for another town as the Professor arrives. He proposes to marry to keep her. This leads first to her laughing, but ultimately to the couple marrying.

Wedding music is played as the two have a reception with all of the other members of the traveling show. The Magician then makes eggs appear from the Professor's nose to the delight of everyone. The eggs cause Lola to begin clucking like a chicken, in turn causing the Professor to crow like a rooster.

Early in the relationship the Professor sees some postcards spilling from Lola's suitcase, which he objects to strongly. He states that as long as he has a penny to his name, they will not sell those postcards. Lola keeps them just in case, which turns out to be not too much later as the next time the Professor is shown he is selling the postcards at a show. This is the first scene in which the Professor is shown as being lower than the others in this group. He has fallen from his former position and is now just the person that fails to sell postcards at show. Even Lola begins to talk down to him at this time. The Professor seems to be at his breaking point and leaves during the humiliating talk aimed at him by the others in this group. However, he quickly returns to Lola.

Lola has the Professor assist in getting her ready for the next show. He takes her curler and burns a page of a calendar. This signifies the passage of time, which changes from days to the year 1925 to the year 1929. The Professor is now playing with clown make-up and appears to be a shadow of his former self as he applies a clown nose and wig in front of a mirror. It now seems that he has become the sad clown from earlier in the film.

As the Professor is preparing his costume, the Magician enters to tell him that the next town they will be visiting is the Professor's hometown and that they will be performing at the Blue Angel. The Magician seems to be in extra high spirits because the show is a sell-out because of the top attraction: the former professor turned clown!

The group arrives at the new venue just as some performers are leaving. The Strongman, Mazeppa (Hans Albers) decides to stay a little longer when he sees Lola. Mazeppa is sure he is in love with Lola and pursues her. Lola seems to be faithful to her husband despite Mazeppa's clear interest in her.

Before his big performance the Professor is prepped by the Magician. During this process the Professor just stares coldly into space, a shell of a person just sitting in a chair. The Magician constantly encourages the blank-faced Immanuel to perform well. Meanwhile Mazeppa and Lola walk past the Professor together poking fun at him, which does not stir any emotion in him. Before he can do anything or find the source of the laughter upstairs he must go on stage. Lola even comes downstairs to force the scared-looking Professor onstage.

Finally the Professor makes his big stage debut with the Magician. The confused Clown or former Professor is then humiliated by the Magician who breaks eggs on the Clown's head as he watches Lola flirting with Mazeppa backstage. Finally the Professor appears to crack up mentally, crowing wildly like a rooster at the Magician's command. He continues to crow as he chases Lola trying to kill her. His attack is eventually stopped by a group of men led by Mazeppa. They wrap the Professor up in a strait-jacket.

Once the Professor has finally calmed down the Magician tries to reason with him. The Magician promises to take care of the situation for the Professor after undoing the strait-jacket. Once the Professor is alone he takes a coat and hat and sneaks out. As he sneaks away he hears Lola singing the "falling in love again" song, which is obviously directed at a new man. The Professor slowly stumbles through the streets until he reaches his old school. He rings on the bell until someone opens the door. The Professor stumbles past this person and into his former classroom. He collapses grasping onto his desk, mirroring the scene in which he left the school for the first time. The Man at the door finds the Professor at the desk and attempts to remove him from it, but is unsuccessful. He leaves the Professor grasping the desk as a lone spot light shines on him and bells ring in the background.

Ende.