The two men climb the stairs and Dorian lets Basil in the room upstairs. He lights the lamp and asks Basil again if he really wants an answer to his question. Basil does, so Dorian pulls the curtain from the portrait and shines the light on it, saying he is delighted to show Basil because Basil is the only man in the world entitled to know all about him. Basil cries out in horror when he sees the portrait. He stares at it for a long time in amazement, not believing at first that it is the same portrait he painted all those years ago.
Dorian is leaning against the mantle shelf watching Basil's reaction with something like triumph expressed on his face. Dorian tells him that years ago when he was a boy, Basil had painted this portrait of him, teaching him to be vain of his looks. Then he had introduced him to Lord Henry who explained to him the wonder of youth. The portrait had completed the lesson in the beauty of youth. When he had seen it in the first moment, he had prayed that he should change places with it, never changing and aging, but letting the picture do so. Basil remembers the prayer. He thinks, however, that it must be impossible. He tries to find some logical explanation for the degradation of the beauty of the portrait. He thinks perhaps the room was damp or that he had used some kind of poor quality paints. He says there was nothing evil or shameful in his ideal that he painted that day. This, instead, is the face of a satyr. Dorian says it is the face of his soul.
Basil begins to believe it is true and then realizes what it means. It means that all that is said of Dorian is true and that his reputation isn't even as bad as he is. He can hear Dorian sobbing as he begins to pray. He asks Dorian to join him in prayer. He says Dorian worshipped himself too much and now they are both punished. Dorian tells him it's too late. Basil insists that it isn't. He begins to pray. Dorian looks at the picture and suddenly feels an overwhelming hatred for Basil. He sees a knife lying nearby and picks it up. He walks over and stands behind Basil and stabs him in the neck several times. When he is finished, he hears nothing but blood dripping. He goes to the door and locks it. He is horrified to look at Basil's body.
He goes to the window and sees a policeman outside and an old woman. He tries not to think about what has happen. He picks up the lamp because he knows the servant will miss it from downstairs, and he goes downstairs, locking the door behind him. Everything is quiet in the house. He remembers that Basil was supposed to leave for Paris that night and had even sent his heavy things ahead of him. No one had seen him come back inside after he left his house earlier that evening. No one will begin to wonder about him for months to come. He puts Basil's bag and coat in a hiding place, the same place where he hides his disguises. Then he puts on his own coat, goes outside, and knocks on the door. His servant opens the door and he asks him what time it is. Then he tells him to wake him at nine the next morning. The servant tells him Mr. Hallward came by and Dorian exclaims over having missed him.
Inside his library again, he picks up the Blue Book and finds the name of Alan Campbell. He says this is the man he wants.
The subject of the portrait kills the artist. Here, the fateful triangle among the three main characters of the novel is broken when Dorian Gray murders Basil Hallward. Basil, as much as the portrait, has served as Dorian's conscience. Dorian has avoided Basil over the years of his explorations of the aesthetics of evil. Here, Basil finally comes to him to confront him. The reader finds out all the specific charges against Dorian. He has ruined the reputations of young men and women, some of whom have even committed suicide. He is ostracized by all the best families of London.
Dorian seems relieved to be able to share the horror of the portrait with Basil, but when Basil sees it, recognizing what it means about Dorian, he wants Dorian to change his ways and repent. Dorian cannot face this possibility and kills Basil instead.