Act IV is set in Voynitsky's bedroom, which doubles as the estate office. Chekhov describes it at length in his stage notes: a large table stands by the window, piled with account books and papers; Astrov's drawing table sits to the side; a map of Africa hangs on the wall. Telegin and Marina sit opposite each other, winding stocking wool. Again an unspecified period of time has passed; it is still autumn.
Through the conversation of the nurse and landowner, we learn that Yelena and the professor are departing that evening for Kharkov, not even bothering to pack their things. Marina is relieved that the household will resume its routine. She then asks after Sonya—apparently she is searching for Voynitsky in the garden with Dr. Astrov, fearful that her father might injure himself.
Voynitsky and Astrov then enter, and the former orders the Marina and Telegin out. Astrov asks Voynitsky to return what he took from him, threatening to use force if necessary. Voynitsky responds that Astrov can do what he likes as his friend is now nothing but a fool, a madman. Ironically, he notes that though he might be mad, no one would ever consider a sham professor or treacherous wife mad. He also accuses Astrov of infidelity with Yelena ("I saw you, I saw the way you held her in your arms!"). Astrov thumbs his nose.
The conversation continues: for Astrov, Voynitsky is not mad but "simply eccentric" and, indeed, "being eccentric is the normal condition of mankind." Suddenly Voynitsky buries his face in shame, repeating the refrain from the act previous: "What can I do?" He dreads the many empty years to come, dreaming of a new life and begging Astrov to help him start one. Annoyed, Astrov tells him he can do nothing, that his situation is hopeless, and that, though they were once the only decent, educated men in the district, provincial life has poisoned them both.
Astrov then renews his request for what Voynitsky has stolen, which is apparently a bottle of morphine. Voynitsky can shoot himself if he feels suicidal, but morphine would unnecessarily implicate the doctor. Sonya then enters, and the doctor appeals to her for help. After his daughter pleads with him, Voynitsky surrenders the bottle and crumbles. Astrov prepares to leave.
These final scenes are significant as they show Uncle Vanya asking for redemption; all too clearly, this redemption brusquely is denied to him. Intimately related to this final blow are the themes and motifs we have discussed thus far: estrangement, the memory of a wasted life, and so on.