On a secret visit to the farm while his son is in Paris on business, Monsieur Duval has an opportunity to speak "directly" and "frankly" to Marguerite in the kitchen of the farmhouse. Disapproving, he tells her that if Armand marries her, he will ruin his foreign service career and his entire future as a diplomat. Because of the intolerance of society, he demands that she stop seeing his son:

Monsieur Duval: You see, I know what's been going on here.
Marguerite: Of course, you don't think me worthy of your son. You're right, I'm not.
Monsieur Duval: No. No woman is worthy of a man's love who's willing to let him ruin himself for her as you're doing.
Marguerite: I don't know what you've heard, but it isn't true.
Monsieur Duval: Armand has told me himself that he wants to take his modest fortune out of my hands at once. The reason is obvious, isn't it? Can you deny he wants the money for you?
Marguerite: Whatever the reason, I hope you won't let him have it, Monsieur.
Monsieur Duval: I wish I could believe you're sincere.
Marguerite: A few years ago, I lived on bread and soup. I can manage very well without taking anything from Armand.
Monsieur Duval: I still say what I came here to say. This thing must end at once!
Marguerite: You might as well save your breath, Monsieur.

Although Monsieur Duval condemns her short-term, three month and twelve day relationship with his son, "unsanctified by marriage, unblessed by children or social ties," Marguerite professes her undying love: "I shall love Armand always. And I believe he shall love me always too." Believing in propriety, Duval tactfully argues that "the human heart can't be trusted," and that their foolish, mood-based love is doomed, particularly since it is socially unacceptable. He also argues that his son is sensitive and more vulnerable than other men:

Marguerite: I think I know my own heart better than you can, Monsieur, and I can trust it not to change.
Monsieur Duval: No woman unprotected as you are can afford to give the best years of her life to a man who when he leaves her will leave her with nothing. And who is certain to leave her in the end.
Marguerite: I don't suppose you can understand how any woman, unprotected as you say I am, can be lifted above self-interest by a sentiment so delicate and pure that she feels only humiliation when you speak of such things.
Monsieur Duval: I realize now that you do love him unselfishly. But even so, I say it can't go on.
Marguerite: But it will go on!
Monsieur Duval: Armand is a young man with his way to make, with a career waiting for him. And in his case, he can't serve his best interest by being tied to a woman he can't present to his family or his friends.
Marguerite: Armand is no different than other men.
Monsieur Duval: Oh, come Mme. Be honest. Haven't you found him different? Haven't you found him more sensitive, more loyal? Or am I prejudiced because I'm his father?
Marguerite: No. I know Armand was different.
Monsieur Duval: So you see, as long as Armand loves you, he'll not enter rooms that you can't.
Marguerite: But a man can go back. He can always go back. Monsieur, suppose I told you I have a feeling I shan't live very long.
Monsieur Duval: Well then I scold you for being fanciful and a little foolish. What you probably feel is the melancholy of happiness, that mood that comes over all of us when we realize that even love can't remain at flood tide forever.
Marguerite: Oh Armand, I'm doomed.
Monsieur Duval: With him, you're both doomed. Without a profession of any sort, what can he do, unless he sinks so low, he's willing to let some other man foot the bills for his life with you.
Marguerite: You don't know Armand. He wouldn't say that.
Monsieur Duval: No one knows the man he might become if he loses his self-respect. But I think that's too high a price to pay even for love. I want Armand to enjoy life, not to be sacrificed to it. You see, my son is as dear to me as he can possibly be to you.
Marguerite: Yes, but you have others who are dear to you. I have only Armand. You don't know how I've changed. And he taught me that love is not always selfish, nor goodness dull, nor men faithless. No, no, you can't expect me to give up such love as his.

Armand's father forcefully persuades her to end their relationship of disrepute in a selfless act of sacrifice for the sake of his family. During their painful confrontation, she complains when she realizes what she must do to end her affair with Armand. But then, wanting what is in Armand's best interest, she succumbs to the inevitable and promises to return Armand to his father:

Monsieur Duval: Think what's best for him. Think what you'd want for him if he were your own son. Then think how you're killing his right to a normal life. Try to realize that everything you're ashamed of in your own past would only taint his future. You tell me that you love him. I believe you. That's why I'm able to stand here - a man who's getting old, and ask this great sacrifice of you, as humbly as I'd ask a great favor of a queen. I can give you nothing in return except my thanks, my respect. Please, give him up.
Marguerite: What should I do?
Monsieur Duval: Talk to him. Tell him he must leave you.
Marguerite: I have talked.
Monsieur Duval: Leave him.
Marguerite: (resting her weight on the kitchen table) He'd follow me.
Monsieur Duval: Tell him you don't love him.
Marguerite: He wouldn't believe me. No. I know only one way. And I shan't tell you what it is. (She suddenly sinks to the floor and drops to her knees, her hands on the table.) Ah, I knew I was too happy.
Monsieur Duval: What are you going to do?
Marguerite: Don't let yourself think of it. I'll send him back to you tonight.
Monsieur Duval: How can I ever repay you for all you're doing for me?
Marguerite: (She turns her head and looks up, resolved in her decision.) Make no mistake, Monsieur. Whatever I do, it's nothing for you. It's all for Armand.
Monsieur Duval: I thank you just the same. And I shall never forget what I and my family owe you.
Marguerite: Goodbye, Monsieur. Don't reproach yourself. You've done only what Armand's father should have done. Only don't let him know it. He might hate you. And I don't want that to happen, because he shall need all the courage and comfort you can give him for a long time, I think.

As the elderly gentleman departs, he blesses her inaccurately as "Margaret" Gautier, and kisses her on the forehead. Later, she sobs and weeps as she writes a letter to Baron de Varville. Even Nanine snorts that Marguerite has sold out and given up her happiness by writing the letter to the villainous Baron: "I thought you were so happy at last with Monsieur Duval...I don't know what's in it, but I know the very thought of this one makes you shudder." Marguerite asks for prayers to be said, as she plans to "make my love hate me."

That evening, Marguerite is prepared to deliver the news to a love-struck, youthfully-happy Armand. Wearing a white gown with bare and exposed shoulders, and her hair with tight corkscrew curls, she doesn't melt into his arms when they meet. When she is a bit brittle, distant and quarrelsome, Armand senses something has happened, thinking that she is fickle. Totally unaware of the real reason for her abrupt change in behavior, he proceeds to eagerly tell her of his plans for their simple future, until she convincingly pretends that she no longer loves him, has wearied of him, and is giving him up. Armand does not understand the enormity of her 'loving-to-death' sacrifice - she has doomed herself to the death of their relationship:

Armand: I came back to you happy with good news.
Marguerite: What do you call good news? You've been left a large fortune?
Armand: No Marguerite, but I find I can do as I please with my small one.
Marguerite: Well, don't you touch it. Why, you'll be rich one month, and then have nothing.
Armand: If that's what you're afraid of, you needn't worry. (He extends her down on a couch and entreats her.) We have something better to do with this money than play at being rich, even for a month. Nichette and Gustave are already looking for a house for us.
Marguerite: (She laughs.) (sarcastically and insincerely) Some people, they think two rooms - wonderful. Three rooms - a mansion. And more than four rooms - wicked. (He draws back.) What's the matter?
Armand: That's what I'm wondering. (She pulls him to her with great suddenness. Desperation and anguish register on her face as she rests her cheek next to his.) Oh, darling, darling. I'd begun to think you didn't love me.
Marguerite: (standing up) Perhaps I don't really.
Armand: You told me only last night - you were ready to give up everything for me.
Marguerite: Well, that was last night. You know, people say things they don't mean sometimes at night. Well, life is something besides kisses and promises in the moonlight. Even you should know that.
Armand: (with a stunned, quiet reaction) Yes.
Marguerite: Wasn't one summer all you wanted?
Armand: So you're going to leave me.
Marguerite: Yes.
Armand: (He slowly approaches toward her, clenches his teeth and violently grabs her with desperation.) I can kill for this.
Marguerite: I'm not worth killing, Armand. I've loved you as much as I could love. If that wasn't enough, I'm not to blame. We don't make our own hearts.
Armand: That's true. You're no more to blame because yours can be faithful only a few weeks than I am, because mine will be faithful as long as I live.
Marguerite: Yes, that's how it is.
Armand: (puzzled) It's as if one was to die, Marguerite, and suddenly I dreamed it.

Marguerite spurns him - she prefers her former life of luxury with the Baron: "Baron de Varville is expecting me. At last, I shall see what a great chateau looks like inside." Bewildered, uncomprehending, and innocently confused, Armand watches from the window as she leaves and walks up the hillside and disappears into the moonlight forever - he calls out in disbelief: "Marguerite."

Some undetermined time later at "the newest and finest of all the private gambling clubs in Paris," Armand is cautioned by Prudence that Marguerite will be appearing with the Baron in the evening, and informed that "the Baron has promised to put her affairs in perfect order." Appearing, cool, content and non-spiteful, Armand replies: "The past is dead. Heaven rest its soul - if it had one."

In a black gown, Marguerite accompanies the Baron down the long, circular staircase - her visage gloomy, dark, burdened and uninspired. She drops her fan and almost faints at the sight of Armand - after being ordered by the Baron to pick up her own fan, she asks to return home due to illness. However, they move forward to greet Prudence and Armand, explaining that they arrived late due to attendance at the theatre. Armand summarizes, with haughty sarcasm in his voice, the theme of the play: "the story of a man who loved a woman more than his honor and a woman who wanted luxury more than his love. (To Marguerite) You should have found that very entertaining." Offended by insults, Armand and the Baron challenge each other for high stakes at the baccarat table - Marguerite blames herself, fearing that Armand "may lose everything."

From a side room, Marguerite sends a messenger to summon Armand from the gambling table (identified as "the youngest and the handsomest man") to speak to her. During the gambling duel, the two men spar with each other:

Armand: ...I warn you, lucky in love, unlucky at cards.
Baron: That also means lucky at cards, unlucky in love.
Armand: We shall see.

Armand wins a fortune at the table before being called away to speak to Marguerite. Realizing that "his voice is too cold and his face is too pale," she fears for his life - an innocent at peril with the feisty, impatient Baron. Outraged and agonized, Armand denounces her as a faithless woman who can be bought and sold, but still begs her to reconsider and run off with him. To keep her promise to his father (and knowing secretly that she is ill), she again vows allegiance to the Baron and declines her love for Armand:

Marguerite: Baron de Varville is not a patient man. And you're in the mood to quarrel with him tonight.
Armand: Naturally you don't want to lose your rich admirer, I understand. Your own fortune would fall with him.
Marguerite: Armand, he's not to blame for what happened - that I swear.
Armand: Then how could you do what you did? I'll tell you. Because your heart is a thing that can be bought and sold. Yes, I know you gave it to me for a whole summer, but when it came to a choice, the jewels and carriages he could give you were worth more than my love, my devotion, my life.
Marguerite: Yes, that's true. I'm a completely worthless woman and no man should risk his life for me. For that reason alone, I beg you leave this place at once.
Armand: I will. I will on one condition - that you'll go with me.
Marguerite: No.
Armand: I came back to Paris to tell you that I despise you, and I do. But I love you too. (She falls limp back into his arms.)
Marguerite: No.
Armand: Say you'll go away with me, we'll forget the past. We'll never turn back.
Marguerite: No, no.
Armand: I doubled my fortune tonight at his expense. And when that's gone, I'll work, I'll beg, borrow, I'll steal, but I must be with you always, always.
Marguerite: When I hear you talking such a future, I realize I'm right in doing what I did. Look. Do you suppose we could ever be happy together even if I were free to act as I choose?
Armand: But you are free. We're both free.
Marguerite: I've given a solemn promise never to return to you.
Armand: To whom?
Marguerite: To someone that had the right to ask you.
Armand: To the Baron de Varville?
Marguerite: (painfully lying) Yes.
Armand: Then you do love him. Dare to tell me that you love him. You're free of me forever.
Marguerite: (He grabs her, and she arches her head and neck backwards.) I love him.

In a public outburst to demonstrate his lack of respect for Marguerite, Armand angrily tosses his winnings at her feet:

I accepted her favors because I thought she loved me. I had her make sacrifices for me when there were others who had more to give. But bear witness, I owe her nothing. (With the crumpled wad of bills in his hand, he thrusts them at her.) Take it, come on, take it! Buy camellias, buy diamonds, horses and carriages, buy moonlight, buy a grave! (He throws the bills at her.)

In an ugly quarrel, the Baron calls Armand a "cheat" and is slapped in return - they both accept the challenge of a duel. On the day of the duel after pacing off the distance and firing gunshots, Marguerite is relieved to learn the outcome: "He's safe...but the Baron is wounded." But her ex-lover refused to open and read the letter she had sent to him. Armand must leave the country to avoid arrest for about six months.

Upon his return to Paris, Armand discovers that Marguerite is dying of consumption (tuberculosis) and has been forced to sell her possessions to raise money - mostly to bargain-hunting Olympe. After the duel, the Baron had abandoned her and "has refused to see her." Debt-ridden, Prudence despairs: "Marguerite won't see the Baron or any other man who might help her." During "the bad times," she is cared for by her faithful maid, Nanine.

A kindly, effeminate Gaston also attends to her, bringing her camellias - her favorite flowers. He is disgusted by the vulturish, court-appointed watchdogs camping out in Marguerite's apartment to prevent the possessions of her creditors from disappearing. She cannot forget Armand and tragically discovers she really loves him just when time is running out:

Nothing will do me good any more, Gaston, except Armand's return...That's what I'm waiting for. That's why I live. He will come back, won't he, Gaston?

When the terminally-ill, anguished Marguerite learns from gossipy Prudence that Armand has been back in Paris for a week, but has not been "terribly interested" in visiting her, she abandons hope, resigns herself to her fate, and asks Gaston to send for the priest to deliver last rites. Finally moved to see her, Armand arrives as the rites are ending, fearing it's maybe "too late." Nanine assures the dying woman that there is "good news" - Armand has indeed returned. The scene emphasizes the confinement of Marguerite on her bed. Her weakened, wan face is framed by her pillow - she rallies to get out of bed when she learns her lover has come:

Marguerite: There can't be any good news.
Nanine: But there is. Only you must be calm. You mustn't get excited. He's here Madame. He's come back...
Marguerite: He's back, but he won't come see me.
Nanine: But he has come. He's here. He's here Madame.
Marguerite: (incredulous) He's here? Are you telling me the truth?
Nanine: Yes, yes. (Marguerite becomes joyous and animated.) Oh, be calm. And I'll call him.
Marguerite: No, no. Not yet. (Marguerite worries about her appearance.) He mustn't see me like this, Nanine. Help me to do my...
Nanine: No, no you mustn't think of getting out of bed.
Marguerite: I'll brush my hair. Get me some rouge. Help me, Nanine.
Nanine: No, no, what would the doctor say?
Marguerite: Oh, what does it matter? I must look my... (whispering) Nanine, Nanine, I beg you, Nanine. I must - you must help me, Nanine. Come on. I beg you, Nanine. I beg you.
Nanine: Oh, I shouldn't do this. You don't think he cares for you. Look, he knows you've been ill...
Marguerite: (She struggles while helped to her feet.) You always said he'd come back, didn't you, Nanine?

Reluctantly, Nanine assists and helps the vulnerable Marguerite as she gets out of bed and painfully makes her way to a chair. There, Nanine brings her camellias to pin to her lap, and brushes her hair. Rapturous, impatient, and hoping to look perfect, Camille begs: "I'll be beautiful again when I'll be well again, won't I?...I can't wait. Call him now, Nanine. Call him now."

In an exquisite, classic deathbed scene, she makes a great effort to stand and greet Armand as he enters. Her eyes and face are joyous and bright for their reunion. But in moments, she is exhausted and debilitated - he sweeps his fragile love into his arms as she falls:

Marguerite: It's you. It's not a dream.
Armand: No, it's not a dream. I'm here with you in my arms, at last.
Marguerite: At last.
Armand: You're weak.
Marguerite: No, no. Strong. (She collapses into a chair.) It's my heart. It's not used to being happy.

He babbles to her about his reaffirmation of love and promises to stay with her forever - now that he understands her love-as-renunciation. He plans for their happy future together, beginning with a trip to the country where she can get well. She gains sustenance and power from his ardor and support.

Armand: I've been everywhere trying to forget how much I loved you. When I came back a week ago, I was still determined to forget you. Forget you - as if I could. Forgive me.
Marguerite: Forgive you?
Armand: And to think I couldn't see into this heart I knew so well and see that it was sacrificing itself for me. No good can come to either of us without the other. I know that now.
Marguerite: I know that too.
Armand: And nothing will separate us ever again.The future is ours. My whole life belongs to you. I'll take you far away from Paris where there are no unhappy memories for either of us. Where the sun will help me take care of you and make you well again. We'll go back to the country where we were happy all one summer.
Marguerite: Oh, oh if only we could. If only we could.
Armand: We can, we will as soon as you're well enough.
Marguerite: Well I'm well now. Call Nanine.
Armand: Nanine!
Marguerite: Take me today.
Armand: Yes. Nanine! Nanine. Help Madame to dress. We're going to the country today. Don't worry. I'll take good care of her.

Marguerite falters however - she goes limp and cries that she isn't strong enough. After he calls for the doctor, places her in a chaise and kneels at her side, she experiences sadness for a love that she has lost forever in the temporal world. But she's not self-deluded - her death will release them from an untenable relationship into a more spiritual, mystical relationship.

Marguerite: The doctor? If you can't make me live, how can he?
Armand: No. Don't say such things, Marguerite. You'll live, you must live.
Marguerite: Perhaps it's better if I live in your heart, where the world can't see me. If I'm dead, there'll be no staying of our love.
Armand: (embracing her) Shhh. Don't say such things, Marguerite, even if we can't go to the country today. Think of how happy we were once, how happy we shall be again. (She signals death when her eyes burst open once. She crumbles and falls lifeless, but remains tranquil with a gentle smile on her face.) Think of the day you found the four leaf clover, and all the good luck it's going to bring us. Think of the vows we heard Nichette and Gustave make and that we're going to make to each other. This is for life Marguerite. (He looks at her and notices she has already passed away. He is horrified that this is the end.) Marguerite. Marguerite! No, don't leave me. Marguerite come back. (He buries his face on her breast, weeping.)

The film ends with a final fade-out, close-up shot of Marguerite's lovely, radiant face - imperishable in death.