Act I
Pyotr Sorin is a retired senior civil servant in failing health at his country estate. His sister, actress Irina Arkadina, arrives at the estate for a brief vacation with her lover, the writer Boris Trigorin. Pyotr and his guests gather at an outdoor stage to see an unconventional play that Irina's son, Konstantin Treplev, has written and directed. The play-within-a-play features Nina Zarechnaya, a young woman who lives on a neighboring estate, as the "soul of the world" in a time far in the future. The play is Konstantin's latest attempt at creating a new theatrical form. It is a dense symbolist work. Irina laughs at the play, finding it ridiculous and incomprehensible; the performance ends prematurely after audience interruption and Konstantin storms off in humiliation. Irina does not seem concerned about her son, who has not found his way in the world. Although others ridicule Konstantin's drama, the physician Yevgeny Dorn praises him.
Act I also sets up the play's various romantic triangles. The schoolteacher Semyon Medvedenko loves Masha, the daughter of the estate's steward Ilya Shamrayev and his wife Polina Andryevna. However, Masha is in love with Konstantin, who is in love with Nina, but Nina falls for Trigorin. Polina is in an affair with Yevgeny. When Masha tells Yevgeny about her longing for Konstantin, Yevgeny helplessly blames the lake for making everybody feel romantic.
Act II
A few days later, in the afternoon, characters are outside the estate. Arkadina, after reminiscing about happier times, engages in a heated argument with the house steward Shamrayev and decides to leave. Nina lingers behind after the group leaves, and Konstantin arrives to give her a gull that he has shot. Nina is confused and horrified at the gift. Konstantin sees Trigorin approaching and leaves in a jealous fit.
Nina asks Trigorin to tell her about the writer's life; he replies that it is not an easy one. Nina says that she knows the life of an actress is not easy either, but she wants more than anything to be one. Trigorin sees the gull that Konstantin has shot and muses on how he could use it as a subject for a short story: "The plot for the short story: a young girl lives all her life on the shore of a lake. She loves the lake, like a gull, and she's happy and free, like a gull. But a man arrives by chance, and when he sees her, he destroys her, out of sheer boredom. Like this gull." Arkadina calls for Trigorin, and he leaves as she tells him that she has changed her mind – they will be leaving immediately. Nina lingers behind, enthralled with Trigorin's celebrity and modesty, and gushes, "My dream!"
Act III
Inside the estate, Arkadina and Trigorin have decided to depart. Between acts Konstantin attempted suicide by shooting himself in the head, but the bullet only grazed his skull. He spends the majority of Act III with his scalp heavily bandaged.
Nina finds Trigorin eating breakfast and presents him with a medallion that proclaims her devotion to him, using a line from one of Trigorin's own books: "If you ever need my life, come and take it." She retreats after begging for one last chance to see Trigorin before he leaves. Arkadina appears, followed by Sorin, whose health has continued to deteriorate. Trigorin leaves to continue packing. After a brief argument between Arkadina and Sorin, Sorin collapses in grief. He is helped off by Medvedenko. Konstantin enters and asks his mother to change his bandage. As she is doing this, Konstantin disparages Trigorin, eliciting another argument. When Trigorin reenters, Konstantin leaves in tears.
Trigorin asks Arkadina if they can stay at the estate. She flatters and cajoles him until he agrees to return with her to Moscow. After she has left the room, Nina comes to say her final goodbye to Trigorin and to inform him that she is running away to become an actress against her parents' wishes. They kiss passionately and make plans to meet again in Moscow.
Act IV
It is winter two years later, in the drawing room that has been converted to Konstantin's study. Masha finally accepted Medvedenko's marriage proposal, and they have a child together, though Masha still nurses an unrequited love for Konstantin. Various characters discuss what has happened in the two years that have passed: Nina and Trigorin lived together in Moscow for a time until he abandoned her and went back to Arkadina. Nina gave birth to Trigorin's baby, but it died in a short time. Nina never achieved any real success as an actress, and she is currently on a tour of the provinces with a small theatre group. Konstantin has had some short stories published, but he is increasingly depressed. Sorin's health is still failing, and the people at the estate have telegraphed for Arkadina to come for his final days.
Most of the play's characters go to the drawing room to play a game of bingo. Konstantin does not join them, instead working on a manuscript at his desk. After the group leaves to eat dinner, Konstantin hears someone at the back door. He is surprised to find Nina, whom he invites inside. Nina tells Konstantin about her life over the last two years. Konstantin says that he followed Nina. She starts to compare herself to the gull that Konstantin killed in Act II, then rejects that and says "I am an actress." She tells him that she was forced to tour with a second-rate theatre company after the death of the child she had with Trigorin, but she seems to have a newfound confidence. Konstantin pleads with her to stay, but she is in such disarray that his pleading means nothing. She embraces Konstantin, and leaves. Despondent, Konstantin spends two minutes silently tearing up his manuscripts before leaving the study.
The group reenters and returns to the bingo game. There is a sudden gunshot from off-stage, and Dorn goes to investigate. He returns and takes Trigorin aside. Dorn tells Trigorin to somehow get Arkadina away, for Konstantin has just shot himself.
