In the salon of her house, Violetta Valéry, one of the stars of the Parisian demi-monde, receives guests for the evening. Alfredo Germont is announced, and is introduced to the lady of the house as an ardent admirer of hers. Baron Douphol, Violetta's lover of the moment, sees the young man as a potential rival for Violetta's affections. Alfredo proposes a toast to the power of love, and Violetta responds with a verse singing the praises of pleasure and amusement. While the guests proceed to the ballroom to begin dancing, Violetta has a dizzy spell, and stays behind. She suddenly finds herself face-to-face with Alfredo, who declares his sincere love for her without further ado. The young woman, who has hitherto only known love from its realistic, down-to-earth side, is surprised and confused by Alfredo's selfless and passionate declaration of love, and says he would do better to forget her, since she can only offer him her friendship. However, she hands him one of the camelias from her decolleté and gives him permission to return when the flower has died. Alfredo understands this as her way of saying he may see her again tomorrow. Left alone, Violetta is assailed by conflicting feelings. She admits that she longs to give and receive love, but when she starts to think that these feeling are taking possession of her, she declares them to be mere silliness and tries to banish all thoughts of love from her mind. Alfredo's voice, heard in the distance, makes her pause for a moment - but then she insists once more that she won't give up the way of life that she knows so well, a life of endless pleasure and dissipation.
Several months later. Violetta and Alfredo have been living quietly on a country estate near Paris. Alfredo is overjoyed at his life together with his beloved, until he learns from the maid Annina that Violetta has gradually been selling all her property in Paris in order to pay for their carefree lifestyle. He is utterly shocked, and sets out for Paris, reproaching himself bitterly for his thoughtlessness, to set things to rights. Violetta has received an invitation from Flora to attend a masked ball, but she is not interested. A visitor is announced. Violetta tells her servant to bring him in, expecting it to be the estate agent - and is surprised when the visitor introduces himself as Giorgio Germont, Alfredo's father. He starts to shower reproaches on her, for he believes that his son is wasting his fortune on a courtesan; but Violetta is able to prove that she is paying all the expenses herself. Giorgio explains that his daughter's marriage will be at risk if Alfredo's way of life continues to damage the family's reputation, and asks her to give up Alfredo. At first, Violetta thinks that Giorgio just means a temporary separation; but then she realises that he wants her to give up Alfredo forever. Germont reminds her that she is living in sin, and foretells that as her beauty fades, so Alfredo's love for her will fade too. He is moved to see her grief, while Violetta agrees to give up Alfredo. She now asks him to leave, and he does so, thanking her sincerely for the sacrifice she is willing to make. She writes a note to Flora accepting the invitation to the ball, then her farewell letter to Alfredo. At this point, Alfredo returns and announces his father's visit. The distraught Violetta, laughing and crying at the same time, throws herself into his arms and assures him that she still loves him then she rushes out of the room. A messenger appears as soon as Violetta has gone and gives Alfredo her letter of farewell. Alfredo's father attempts to console his son and asks him to return to the family. Alfredo is completely stunned by what has happened, and by the premonition that Violetta is going to resume her former way of life. Then he espies Flora's invitation on the table, and hastens off in pursuit of the (as he believes) disloyal Violetta. In Flora's house, the guests are already arriving. The news begins to spread that Violetta and Alfredo have broken up, when Alfredo himself appears and plunges into the activity of the masked ball. Asked about Violetta, he shrugs his shoulders and takes a seat at the gambling table. When Violetta appears on Baron Douphol's arm, she observes how Alfredo - to the growing annoyance of the Baron - is making suggestive remarks in her direction. Douphol joins his rival at the card table, and soon loses a considerable sum of money to him. Before the tension between the two men escalates further, the guests are summoned into the dining room. Violetta returns, followed by Alfredo. She asks him to leave the ball before he starts to quarrel with the Baron. Alfredo cynically implies that she is afraid for her protector, but adds that he is prepared to leave if she accompanies him. Since she won't agree Alfredo forces her to admit that she loves Douphol. He then recalls the guests and announces to the assembled company that Violetta squandered her fortune on him. To reward her for the favours he enjoyed, he flings his winnings from cards at her feet. The guests are indignant, and Violetta sinks unconscious into Flora's arms. Father Germont arrives on the scene too late and criticizes his son's behaviour. The Baron for his part demands satisfaction from Alfredo, who already regrets his vindictive action, while Violetta regains consciousness and laments that she cannot open her heart to her beloved. But she knows that he will forgive her one day.
Violetta lies in bed in her Paris apartment; she is seriously ill, and Annina is looking after her. The doctor promises Violetta that she will get better soon, but he takes the maid to one side and admits that her mistress only has a few hours left to live. As the noise of the carnival is carried up to her ears from the street below, Violetta feels the end of her life approaching. A letter >From Alfredo's father informs her that Alfredo wounded the Baron in a duel, and was forced to flee the country for a while. He has told his son at last about the sacrifice Violetta made, and Alfredo and his father are now both on their way to her to ask her forgiveness. A glance in the mirror tells Violetta that it is too late for any hope, and she bids farewell to the happy dreams she nurtured in the past. Alfredo rushes into the room and sinks into Violetta's arms. For one brief moment, the two lovers forget their hopeless circumstances, and dream of a future together. Although the longing to cling on to life flares up in Violetta one last time, her strength finally deserts her as she tries to get out of bed. Violetta makes Alfredo a parting gift of a locket containing her picture. She says he should keep it to give to the girl who will love him one day, as a present from someone who will be praying for both of them. All of a sudden, Violetta seems to be miraculously cured of her pain, and sits up in bed with a last ray of hope - then she sinks back lifeless into Alfredo's arms.