The opera opens on a party in the salon of Violetta Valery, a young courtesan of great beauty. Among the guests is Alfredo Germont, who proposes a toast to the gaiety of the affair. The guests swirl off to another room to dance, but Violetta, seized with a coughing fit, sinks to a sofa. Alfredo comes to her, and tells her that, although he has seen her only from a distance, he is seriously in love with her. Violetta advises him to forget about her, but finally promises to see him the next day.

When the guests are gone, Violetta remembers Alfredo, and asks herself if this young man might be the one true love in her life of many affairs. But no, she reminds herself, such love is not for her. She must remain forever free.

Violetta has succumbed to Alfredo’s ardor and the two are living in a house outside Paris. Alfredo’s happiness is shaken when he learns from Violetta’s maid, Annina, that she has been selling her personal belongings to pay for their life together. He rushes off to Paris to try to raise money.

Violetta is expecting her lawyer, and when a caller is announced, asks that he be shown in. But it is Alfredo’s father who enters. He pleads with her to leave Alfredo, for not only is the young man’s own career threatened, but his sister’s impending marriage is endangered by this dubious liaison. Heartbroken, Violetta agrees to arrange things so that Alfredo will believe she has tired of life with him, and writes a farewell note, which she gives to Annina. Another note to Flora Berviox accepts the invitation to a party that night at the salon of her old friend.

Before she can escape, Alfredo returns. Violetta begs him to love her always, and quietly steals away. A moment later Annina brings him the farewell note in which Violetta says she has gone back to her former protector, Baron Duphol. Alfredo is about to follow her, when his father re-enters. The older man reminds his son of their peaceful home, and begs him to return there with him. But Alfredo has found Flora’s invitation and resolves to follow Violetta to the party to avenge the insult.

In Flora’s salon, gypsy dancers are entertaining the party guests. Alfredo enters alone and shortly afterward Violetta comes in on the Baron’s arm. At the gaming table Alfredo wins again and again until he has almost wiped out the Baron. As the guests go off to supper, Violetta stays behind to beg Alfredo to leave before trouble starts. Alfredo tells her that he will leave if she goes with him, and demands to know whether she is in love with the Baron. Remembering her promise to the elder Germont, Violetta tells him she is. At this, Alfredo summons the guests to hear his denunciation of Violetta, and hurls his winnings in her face.

Some months have elapsed, and Act IV finds Violetta living in a shabby flat, desperately ill, attended only by the faithful Annina. Dr. Grenvil calls with cheering words, but tells Annina that Violetta can live only for a few hours. Germont has written, saying that he has told Alfredo of her sacrifice, and promising to bring the young man to her. Violetta knows that death is very near, and remembers the happy past. Suddenly Alfredo rushes in. Reunited, the lovers plan to leave the city together. But it is too late – Violetta cannot even struggle into her clothes. Annina rushes for the doctor, and the elder Germont enters to hear Violetta give Alfredo a miniature portrait of herself and charge him to give it to his future bride. As Violetta falls back in her lover’s arms, the doctor arrives, only in time to tell them that all is over.