She returns to Vienna where she makes her own way as a dressmaker's mannequin or model in a fashion salon - intent on seeking a reunion with Stefan:

Vienna, when I saw it again, seemed to have taken on a new splendor. All the time I'd been away I thought of it longingly as your city. Now it was our city. Madame Spitzer's, where I found work, was the kind of establishment where one learns many things.

A montage of short scenes illustrate how she is on display - and often noticed on- and off-stage, but she shuns attention. From the back room where she is costumed with a garment, she emerges in the front showroom to display a new dress for customers. She seeks privacy one evening when uniformed officers on the sidewalk stare in the window at her. And another day while she models a gorgeous white gown, an old lecherous officer is followed by the camera as he crosses the dressmaker's display room, from where he has left his wife, to consult with Madame Spitzer at her desk and ask: "Very charming. Very charming, indeed. Do you think...?" Madame Spitzer stresses to the obviously-disappointed gentleman that her employee is unavailable:

She's not like the others. I don't understand that girl, but every evening as soon as the shutters are closed, off she goes - straight home.

In one of the most jarring voice-overs, as Lisa leaves her place of work later that evening, she confirms what she appears to have overheard from Madame Spitzer: " Madame Spitzer spoke the truth. I was not like the others. Nobody waited for me." Every night after work, Lisa seeks out Stefan at his residence by standing across the street from his apartment, hoping to be noticed:

Off I went, not home, but to the only place that had ever seemed home to me. Night after night... I returned to the same spot, but you never noticed me until one evening...

On a snow-covered street corner next to a wall, Lisa stands and then sees Stefan casually walking and passing by with his hands in his overcoat pockets. He offers money to a small boy among a group of street musicians and then notices her watching him. As he approaches her, he removes his hat and mentions that he has seen her before, "a few nights ago...right here." As they talk, Lisa is embarrassed and looks down. As they walk along, he proposes to introduce himself, but Lisa informs him: "I know who you are."

Attracted by her beauty and her availability, he takes her arm and leads her into a nearby restaurant, the Schoholado Liqueur. There, Stefan speaks with maitre d' Fritz (William Trenk) to arrange two conspiracies - he calls off his evening's rehearsal, and also prepares an alibi for Lelia if she comes looking for him. He takes Lisa in a carriage to an opulent restaurant, and ties a "becoming" lobster napkin around her neck. Then, because she has "no engagements at all" during the next week, he asks to have dinner with her the next night - wienerschnitzel.

Lisa is enamoured of Mr. Brand, telling him that she remembered when he played the D Minor four years earlier, and the Morning Review compared him to a "young Mozart." She asks him: "Please, talk about yourself," and then he realizes that she has been very quiet: "You know, you don't talk very much."

Lisa: Well, I can't say it very well, but...sometimes, I felt when you were playing that...that you haven't quite found - I don't know what it is - what you're looking for.
Stefan: How long have you been hiding in my piano? Never mind explaining. I'll just assume you're a sorceress and that you can make yourself very tiny. (Lisa laughs.) It might be a good thing to have a sorceress for a friend. Who knows, you may be able to help me someday.

In the back seat of an open carriage as they ride along after dinner, their conversation continues as Lisa looks at him and asks:

Lisa: How could I help you?
Stefan: So that's what you've been thinking about. (She smiles and sighs.) You're a very strange girl, whoever you are and wherever you came from. Don't you have any problems?
Lisa: Not important ones.

After she reaches over and tucks his scarf into his overcoat, he thanks her: "It's a long while since anyone did that for me." At a flower stand, he purchases a "single, white rose - that's perfect!", telling the flower seller: "This is a special occasion." He presents Lisa with the rose:

Stefan: Did I guess right? Is it your flower?
Lisa (gazing lovingly at the rose): From now on, it will be.

At the Viennese fairgrounds (Prater Park), they walk in the snowy landscape, as carnival music plays on the soundtrack and a large ferris wheel is seen in the background. There, in a setting of old-world Vienna, the theatrical sets in the wintry setting remind them of how illusory life can be:

Stefan: I never come here in the season. It's more pleasant in the winter. I don't know why.
Lisa: It's perhaps because you prefer to imagine how it will be in the Spring because if it is Spring, then there's nothing to imagine, nothing to wish for.
Stefan: Is there anything about me you don't know?
Lisa: A few things.

In front of a glass case containing famous historical wax figures, Lisa wonders if she will see him someday:

Lisa: For instance. I don't know if one day, they'll make a wax figure of you and put you in there because you'll be so famous.
Stefan: Well, if they do, will you pay your penny to come in and see me?
Lisa: If you'll come alive.

At the carnival, two confectioners in parkside booths sell their wares high off the ground - a taffy vendor stretches the taffy, and a man prepares a carmel apple which he extends in a shuttle basket to Lisa. She smiles as she holds the apple:

Stefan: Now I see you as a little girl.
Lisa: You do?

Seated in a mock railroad car during a magical rolling-canvas cyclorama ride, with painted scenery passing across the large curtained window between them, the musical soundtrack plays the hurdy-gurdy melody "The Carnival of Venice." Awkwardly girlish, Lisa fondles her single white rose. She explains her imaginary travels with her father to places with various climates around the globe when she was younger - and when she looked at pictures from the travel bureau with him:

Lisa: When my father was alive, we traveled a lot. We went nearly everywhere. We had wonderful times.
Stefan: I didn't know you traveled so much.
Lisa: Well, yes.
Stefan: Perhaps we've been to some of the same places.
Lisa: No, I don't think so.
Stefan: Where did you go?
Lisa: Well, it was a long time, but...for instance, there was Rio de Janeiro, beautiful exotic Rio with its botanical gardens, its Avenue of Palms, Sugar Loaf Mountain, and the harbor where you could look down and see the flying fishes. (She turns and looks at the painted scene behind them) We're in Venice.
Stefan: Yes, we've arrived. Now, where would you like to go next? France? England? Russia?
Lisa: Switzerland.

Stefan obliges her wish (to arrange another illusion) by exiting the closed compartment and walking about a dozen steps to the ticket kiosk to ask the old woman to arrange for a visit to Switzerland. After he turns away, the woman calls out to her husband - the cyclorama cyclist/engineer - to pedal a stationary bicycle to move the slowly-rolling canvas outside the compartment's window with a new backdrop. [This is one of the best examples of how the film includes an incident absent from the characters' experience.] When their journey commences again, Stefan moves across the compartment and sits next to her, holds her hand, and then pulls her to him. When the ride abruptly ends and they run out of countries to visit, Stefan pays for another one so they can "revisit the scenes of our youth" in the compartment.

In the next dissolve, they are found waltzing in front of a uniformed, all-female orchestra within a deserted dance-hall. One of the female musicians cynically complains to the pianist about being kept late: "I like to play for married people. They've got homes." When they stop dancing, Stefan applauds and then tells Lisa:

You are a sorceress. Now, I'm sure. How else could we dance this way unless we've danced together before? (She looks down, but he raises her chin with his finger.) And yet if we had, I should have remembered.

The bandstand has been quickly vacated by the musicians, so Lisa motions Stefan to play the same waltz on the piano that the orchestra had just been playing. In a beautifully-framed sequence, Lisa makes her way toward him as he plays, first leaving her jacket, purse, and white rose on a table, and then moving to stand next to a post near him. As a man extinguishes the lights on the posts in the dance floor area, Lisa kneels with her face next to the keyboard:

Stefan: Promise me something.
Lisa: Anything.
Stefan: And I don't even know where you live. Promise me you won't vanish.
Lisa: I won't be the one who vanishes.

In an exquisite close-up of her loving face, she looks up adoringly at Stefan and then at his fingers as they glide over the keys.

Following an evening of courtship, a carriage takes them back to Stefan's apartment, where they arrive in the early-morning hours. The concierge again asks: "Who is it?" and Brandt identifies himself. They are familiarly viewed in a high-angle camera shot from the landing above the hall stairway. [This scene is connected to the shot when Lisa was eavesdropping on him years earlier with another lady friend, another 'unknown woman.' One main difference is that the scene is more solemn this time. Giggling or furtive whispering, that indicates a disreputable or illicit association, has been replaced by romantic waltz music on the soundtrack.] Stefan slowly escorts the lovelorn girl, wearing a plain black coat and hat, up the winding stairs to the door of his apartment. She hesitates/pauses for a brief moment at the top of the stairs before committing to him. [Rather than watching another's seduction, she now participates in its enactment.] The camera cuts to the inside of the apartment, where she surrenders to him in his arms as he kisses her passionately. The music swells and the screen fades out to black.

The next day in the dress salon, introduced by closed draperies, Madame Spitzer bursts through the sealed-off backstage area where she asks Lisa to model for a "new customer" who "looks like a good one" - it is Stefan. Madame Spitzer readies the gentleman for a viewing: "You will like this one, I'm sure." Explaining that he was "a good detective" to have found her, Stefan also tells her that he must put off their plans for the night because he is going on a two-week concert tour to Milan to play at La Scala. He requests that she see him off at the train station at 5:30, and then turns back to look at her once more from the door: "Goodbye. You'll be there?"

Getting off work early, Lisa rushes to the train station and sees him surrounded by a crowd of people just before the train pulls away. He walks away from the crowd and takes her hand while looking intently into her eyes:

Stefan: I don't want to go. Do you believe that?
Lisa: I'll be here when you get back.
Stefan: (A female voice calls out for Stefan to hurry.) ...I still know so little about you.
Lisa: You like mystery. (She looks down.)
Stefan: That a woman like you exists, and I've found you, that's mystery enough. Say 'Stefan' the way you said it last night.
Lisa: Stefan.
Stefan: It's as though you said it all your life...Goodbye (He kisses her hand.)...It won't be long. I'll be back in two weeks. (Lisa smiles and waves as he boards the train just in time.) Goodbye. Two weeks!

With the piercing sound of violins, Lisa watches as the train pulls away, then looks down, turns away and begins to cry after the emotional farewell. The image blurs and dissolves with Lisa's voice-over in the recitation of the letter:

Two weeks. Stefan, how little you knew yourself. That train was taking you out of my life.

A nun in habit walks down a hallway toward the camera, holding a lit candle in front of her. She enters a doorway where there is a ward of curtained bedchambers. Above one of the curtained enclosures is a chalkboard on which is written:

Name: Stefan
Born: 12 November
Mother: Lisa Berndl
Father:

A nun's voice off-screen questions Lisa as she lies in a bed in one of the darkly-lit chambers:

Nun's Voice: He was a married man? Does he live here in Vienna? If we knew who he was, he might be willing to accept his responsibility. You won't tell us his name? (Lisa shakes her head) But you haven't the means to take care of the child.
Lisa (weakly): We'll get along.
Nun: It's your duty to tell us. When a man does this sort of thing...
Lisa: I'm feeling tired. Would you go?

The scene at the charity hospital following Lisa's unwed pregnancy and birth dissolves and then returns to the scene of Stefan reading the letter at his desk. After vanishing from his life, Lisa explains her vow of silence and her refusal to speak about her son:

You may wonder why I never came to you for help. I wanted to be one woman you had known who asked you for nothing. My deep regret is that you never saw your son. (Stefan looks at a picture of a small boy with a magnifying glass - probing to know more about a son he will never meet.) There were times during those years I prefer not to remember. But this I can assure you... (Stefan looks at a second picture of a slightly older boy in a mock hot air balloon with Lisa.) whatever the cost, he repaid me a thousand times. You would have been proud of him, too. When he was about nine...(Stefan looks at a third, more formally-posed picture of an even older boy.) as much for his sake as mine, I married. You know who my husband is. Johann Stauffer married me, knowing the truth about us and about our child.

Years later after being abandoned and forgotten by Stefan Brand, Lisa is married to a wealthy, middle-aged Austrian aristocrat named Johann Stauffer (Marcel Journet) - he accepts her illegitimate son and provides protective security for her. They live in an expensive mansion, and Lisa, now more mature and sophisticated, wears expensive pearls, a white gown, and a white fur coat as she prepares to go to the opera with her affectionate husband. Their young son Stefan, Jr. (Leo B. Pessin) is thought to "have a natural talent...for music" by Herr Frank, his music teacher. Stefan still calls his step-father "sir" instead of "father."

At the opera house where Mozart's "Die Zauberflote" is to be performed and opera-goers mill about between acts, Lisa's voice-over is heard as the camera wanders (in an amazing crane shot) through groups of people in the lobby. She speaks of the forces of Chance and Destiny, that nothing happens by chance:

The course of our lives can be changed by such little things. So many passing by, each intent on his own problems. So many faces that one might easily have been lost. I know now that nothing happens by chance. Every moment is measured; every step is counted.