It is Christmas Eve. From the garret window, Rodolfo gazes at the snow-covered rooftops of Paris, while Marcello works on a painting. Numb with cold, Rodolfo curses the dismal fireplace. Marcello suggests they warm it up by sacrificing a chair, but Rodolfo prefers to burn the manuscript of the tragedy he is working on. When Colline enters, he too tries to warm himself by the ashes of the fire. After a while, however, Schaunard arrives with food, firewood, cigars and wine, which he has received in payment from a rich English lord. The four friends decide to celebrate in the Latin Quarter. There is a knock at the door. Benoît, their landlord, has come to collect the rent. The four welcome him in, ply him with drink and flattery until, pretending to be scandalized by his amorous adventures, they send him packing. Marcello, Schaunard and Colline go out, while Rodolfo, who has to finish an article, lingers in the room. A timid knock is heard at the door and Mimì, their neighbour, comes in. Her candle has gone out. Seeing her gasping for breath after climbing the stairs, Rodolfo offers her a seat and a drop of wine, as he contemplates her pallid face. Having regained some strength, Mimì is about to leave the attic when she realizes she has dropped the key to her room. Rodolfo helps her look for it, but when he finds it he slips it into his pocket, so that the girl will stay with him a little longer. He takes her hand and briefly tells her his story. He is a poor poet who scrapes a living. Mimì replies by recounting her own life and confiding her dreams to him. Rodolfo kisses her and offers her his arm as they go off to the Latin Quarter.
In the Latin Quarter, pushing their way through the criss-cross of narrow streets crowded with people and vendors, the four friends head for the Café Momus. Rodolfo gives Mimì a pink bonnet and introduces her to his friends. From a distance, Marcello sees Musetta, with whom he has argued but is still in love. Escorted by the old state councilor Alcindoro, Musetta catches sight of Marcello, who pretends not to notice her. She behaves coquettishly and sings a provocative waltz tune. Making fun of Alcindoro, she pretends that her shoes are hurting, and dispatches him to buy her a new pair. Reconquered, Marcello approaches Musetta and takes her in his arms. When the old councillor returns, he finds himself alone with a large bill to be settled.
Sometime later. Early on a cold winter’s morning, the customs officers open the Enfer city gate to let in road sweepers, carters and peasant women. From the interior of a cabaret are heard the sounds of loud laughter. Mimì now also arrives at the gate, suffering from fits of coughing. She asks for Marcello, who comes out of the cabaret and is surprised to see her there. The girl confides her decision to separate from Rodolfo, whose jealousy is making her life impossible. Mimì hides when she sees Rodolfo come out of the cabaret, who confides to his friend the real reason for their parting, which is that he cannot afford to offer Mimì, whose health is ruined by consumption, the assistance she needs. Mimì, who has heard all, reveals her presence and Rodolfo embraces her tenderly. On hearing Musetta’s impudent laughter, Marcello rushes back into the cabaret. Mimì bids farewell to Rodolfo, leaving her pink bonnet as a memento. But the two cannot bring themselves to part, and decide to stay together until April, when the blossom will be out. Meanwhile Musetta and Marcello argue bitterly.
Some weeks later, Rodolfo and Marcello attempt without success to concentrate on their art. However, their minds are heavy only with thoughts of Mimì and Musetta, who are both absent. The two friends are trying to dissimulate their sadness when Schaunard and Colline arrive, bringing a few meagre supplies. The quartet pretend to feast cheerfully with what little they have. But the scene is interrupted by the sudden entry of Musetta, who has brought with her Mimì, now desperately ill. Rodolfo lowers Mimì onto the bed and clasps her hands to warm them. Musetta sends out Marcello to sell her earrings to buy a cordial and to call a doctor, while she herself goes off to look for a muff. Colline sacrifices his old overcoat and goes out with Schaunard to pawn it. Mimì is left alone with Rodolfo, to whom she makes her last heartrending declaration of love. Together they remember the happiness of their first encounter, when Mimì realized that Rodolfo had hidden her key but pretended she had not noticed. Their friends reenter. Mimì drowses and gently dies, leaving Rodolfo in despair.