In the Russian countryside in July 1896, Dr. Mikhail Astroff arrives at the estate of the aging Professor Alexander Serebryakov, who is plagued by gout. Meeting with elderly nurse Marina in the garden, Astroff reflects that he has been visiting the estate for more than eleven years, and has grown bored by the unvarying dullness of country life. Ivan Petrovich "Vanya" Voynitsky, the professor's brother-in-law from his first marriage, and the manager of the estate, joins Astroff and Marina, and describes the dreary daily routine of the querulous Serebryakov. Despite his fondness for his niece, Sonia, Vanya remains critical of her father's torpid lifestyle. Just then Serebryakov, his second wife Elena and Sonia arrive in the garden and Vanya comments on the injustice of an old man having such a young and beautiful wife. Vanya's mother Maria and family friend, Ilya Ilyich Telegin, a poor but pleasant man who works on the estate, join the others and Maria nags Vanya about his unsuccessful financial management of the estate. Before departing to tend to a local patient, the doctor casually invites Elena to visit him some time at his secluded home deep in the forest. Despite Elena's cool response, Astroff describes the beauty of nature and the unfortunate tendency of man to destroy it. Annoyed by Astroff's patronizing air, Elena mocks his fondness for nature, prompting Sonia, who secretly admires Astroff, to protest. After the doctor's departure, Elena chats with Vanya, expressing her puzzlement over the village's constant gossip about her marriage to a much older man. Overcome by Elena's nearness, Vanya declares his love for her, but Elena remains completely indifferent. Two weeks later, during an evening rainstorm, Serebryakov petulantly accuses his wife of being repelled by his old age and suspects that his family is only waiting for him to die. Sonia enters the study and chastises her father for summoning Astroff, then refusing to see him. Serebryakov dismisses Astroff as incompetent and continues his grievance about being disregarded by his family, until placated by the soothing Marina. A little later, Vanya again makes overtures to Elena only to be rebuffed. In private Vanya wonders what his life might have been had he rather than Serebryakov married Elena. Meanwhile, Astroff and Telegin have consumed several glasses of vodka and Telegin plays his guitar and sings. Astroff drunkenly tells Sonia that her father refuses to follow his medical advice and is wallowing in his stagnant existence while Vanya foolishly pursues Elena, who remains oblivious and self-absorbed. Sonia pleads with Astroff not to drink and points out that he is behaving like the ignorant peasants of whom he is so critical. Startled, Astroff reflects that life is passing him by and then comments upon Elena's great beauty. Sonia asks the doctor what he would do if a woman fell in love with him, but Astroff declares that he is incapable of loving anyone. That evening, Elena approaches Sonia and the two women, estranged since the professor's marriage, reconcile. Although Elena declares she does indeed love Serebryakov, she admits that she is unhappy. Sonia confesses her feelings for Astroff and Elena cautions her that the doctor is a difficult man. Pleased about their reconciliation, Elena offers to play the piano for Sonia if her husband will allow, but Serebryakov refuses. By September, little has changed at the Serebryakov estate. Continually bored, Elena laments the coming winter. When Sonia stoically confides that she has given up all hope that Astroff will notice her, Elena offers to ask Astroff about his feelings. Upon reflection, Elena realizes her own attraction to Astroff, but, when alone with the doctor, as promised, asks him if he cares for Sonia. Perplexed, Astroff confesses that he believes his time for happiness has passed. Abruptly suspecting that Elena is only flirting with him, Astroff criticizes her for her selfish, spoiled existence, yet embraces and kisses her. Walking in on the couple, Vanya is stunned, despite Elena's feigned outrage at Astroff's behavior. Astroff departs and Vanya's heartbroken attempt to question Elena is interrupted by Serebryakov's appearance and declaration that he has an announcement. When the household members have gathered, Serebryakov declares his intention to sell the estate and retire to a small country cottage. Shocked and outraged, Vanya angrily objects, reminding the professor that his sister left the property to Sonia. Maria attempts to silence Vanya, but he emotionally proclaims that he has spent his entire life managing the estate and years earlier spent his own money to help his sister pay it off. Vanya then adds that he has worked since his sister's death for a pittance without any acknowledgment from Serebryakov. When Maria refuses Vanya's pleas for support, he storms from the room while the professor remains offended by the outburst. Sonia reminds her father of all the help her uncle has provided in the past and, agreeing to speak with Vanya, the professor goes in search of him. Moments later a gunshot rings out and Serebryakov rushes back into the room, followed by Vanya who waves a pistol at him and fires, missing him again. Distraught, Vanya collapses as Elena demands that her husband take her away. Two hours later, Marina and Telegin discuss the Serebryakovs' impending departure. Astroff appears and demands that Vanya return a missing vial of morphine. When Sonia chastises her uncle for not bearing his despair properly, he gives the morphine to Astroff. Before departing, Serebryakov meets with Vanya to exchange apologies while Elena bids farewell to Astroff. The doctor repeats his invitation to visit him in the forest, but then condemns the Serebryakovs for poisoning the estate with their idleness. Elena and Serebryakov depart, leaving Sonia with her uncle, who remains despondent over Elena's final snub. After accepting a drink offered by Marina, Astroff takes his leave. As Sonia settles into helping Vanya with the bills, she reflects that they will live a long time in poverty and solitude which, in time, will matter to no one.
