A party is taking place at the home of Violetta Valéry, a beautiful Parisian demimondaine. Gastone arrives and presents his friend, Alfredo Germont, telling Violetta that Alfredo has long been a silent admirer and had even called daily during her illness to ask about her. Baron Douphol, one of Violetta’s “protectors,” is angered by the conversation and refuses to propose a toast when invited to by Gastone. Alfredo then accepts the invitation and sings an impassioned tribute to beauty and love. Later, as the others go to another room to dance, Violetta is overcome by a fainting spell. Alfredo stays behind and confesses that he has been in love with her for a year. Violetta offers him friendship instead of love and gives him a flower, bidding him return when it has withered. Alfredo joyously accepts and bids her goodnight. When her guests have gone, Violetta thoughtfully muses on Alfredo’s proffered love, but finally declares that she must remain forever free to pass from pleasure to pleasure.
Months later, Violetta is living with Alfredo in the country, having abandoned her life of ease and luxury in Paris. Annina, Violetta’s maid and confidante, enters and tells Alfredo she has been sent to arrange the sale of Violetta’s property, which must be sold to pay their debts. Alfredo suddenly understands the sacrifices that Violetta has made in order to live with him and leaves for Paris, determined not to be shamed by her sacrifice. Violetta receives an unexpected visitor, Giorgio Germont, Alfredo’s father, who declares that Alfredo is ruining himself to keep her as his mistress. When Germont comments on the luxury of the country retreat, Violetta shows him the papers that have been prepared for the sale of all her possessions. He asks her to give up Alfredo, explaining that by continuing the liaison, Alfredo is endangering the impending marriage of his younger sister. Germont’s insistence finally convinces Violetta, who agrees to leave Alfredo forever. She is preparing a letter as Alfredo returns. Germont has gone out into the garden. Alfredo, not realizing his father has already arrived, explains that Germont has written him a severe letter but that he feels sure he will approve of Violetta as soon as he sees her. Pretending to leave so as not to be present during the meeting of father and son, Violetta goes out. A messenger returns with her letter of farewell. Alfredo is stricken with grief at the loss of Violetta, and when his father tries to persuade him to return to his family, Alfredo refuses. Finding an invitation that Flora had sent Violetta, he resolves to go to Flora’s in the hope of finding Violetta.
Alfredo arrives at Flora’s house as the guests are beginning to gamble. Then Violetta arrives, escorted by Baron Douphol. Alfredo is incredibly lucky at cards and explains that he who is unlucky in love is lucky at cards. The Baron, incensed at Alfredo’s insolence, challenges him to play. Alfredo accepts and beats the Baron repeatedly at high stakes. When all the others go to dinner, Violetta remains behind to entreat Alfredo to leave, lest the Baron challenge him to a duel. Alfredo answers that he will leave, but only if she accompanies him. Unwilling to reveal that she must break off with him because of his father, Violetta declares that she is in love with the Baron. Alfredo, in a frenzy of jealousy, calls all the guests into the room and announces that without knowing it he has been living with Violetta at great sacrifice on her part. In a rage, he throws money at her feet and calls upon all to witness that he has paid her in full. Germont has entered just in time to see Alfredo’s caddish behavior and joins the others in reviling him for his conduct. Alfredo, realizing the lengths to which his jealousy has carried him, is contrite but realizes that he is helpless to make amends. The Baron assures Alfredo that he must answer for the insult on the field of honor.
Violetta’s illness has brought her to the point of death. Her physician, Dr. Grenvil, calls at her home, examines her, and tells Annina that she has but a few hours to live. Violetta reads a letter from the elder Germont, in which she learns that Alfredo has gone abroad after wounding the Baron in a duel. He knows now of the great sacrifice that Violetta has made and is returning to beg her forgiveness. Alfredo returns and the two are reunited at last. But it is too late. Violetta, comforted by the presence of the man whom she has so tragically loved, dies in his arms.