After a brief delay, during which Berenger watches the rhinos out the window, Dudard opens the door for Daisy. Dudard insinuates that Daisy is coming for a romantic rendezvous, but she insists she is just a "good friend." While offering sympathy to Berenger, Daisy also appears not to care too deeply about the epidemic. She informs them that Botard has metamorphosed. Berenger can't believe it, feeling that Botard was fooling them in a disguise. Daisy says Botard's last words were "We must move with the times!" On reflection, Berenger justifies Botard's behavior, indicting his stubbornness as only a pose. Dudard believes Botard was following Papillon, his superior, and both men agree that the rhinoceroses are anarchic, because they are in the minority—"for the moment."

All three discuss the social problems caused by the rhinos—especially the problem of eliminating them. Daisy and Dudard say that acclimating oneself to the rhinos is the best solution, but Berenger resists. They start to have lunch, but are interrupted by a crumbling wall outside. The dust settles and they see that the fire station has been sacked, and that the firemen have turned into rhinos and now march in a regiment, led by drums. Berenger's will seems shaken by the accelerating epidemic. Dudard makes excuses to leave under the guise of politeness. He then reveals that he wants to experience the epidemic first-hand and join the "universal family." Berenger tries to stop him, but Daisy believes in letting him, and people in general, make their own decisions. Dudard soon turns into a rhino outside.

According to the stage directions, the thunderous, thickening stampede (in the form of stylized heads appearing on the wall) creates a "musical sound" and the heads "seem to become more and more beautiful." Berenger makes passionate declarations of love to the nonchalant Daisy. Berenger laments Dudard's demise, and Daisy reminds Berenger that they have no right to interfere in other's lives. As Berenger points out, though, Daisy has assumed control of their own relationship. She explains the difference: as she loves Berenger (and not Dudard), she has the right to interfere in his life. Berenger seizes upon Daisy's admittance of her love for him, pointing out that Dudard would have only been an "obstacle" between them.

Daisy pours some brandy for Berenger, rewarding him for being a "good boy." She removes his bandage—still no signs of a transformation—and they fantasize about their lives together. Berenger claims he will defend her, but Daisy says no one intends them any harm. He replies that we sometimes do harm by simply not preventing harm. He blames himself and Daisy for contributing, through lack of sympathy, to the transformations of Jean and Papillon, respectively. Daisy convinces him to shrug off the guilt; as relatively "good" people, they have a right to happy lives despite the circumstances around them. Berenger agrees, and surmises that guilt is what probably turned a lot of people into rhinos in the first place.

The phone rings, and Daisy cautions Berenger not to pick it up. Berenger answers it, thinking it will be the authorities, but hears only rhino trumpeting from the phone. Daisy hangs it up, frightened. Berenger claims he was expecting the prank rhino-call, and Daisy states that you can only predict things once they've happened. The phone rings again, and they turn to the radio for help, but the rhinos have taken that over, as well. They grow more terrified, aware that they are the last hold-outs.

Upstairs, a rhino stampede sparks eruptions within the house. Now Berenger wants to live a guiltless existence, and offers some brandy to the sunken Daisy, who believes the responsibility for the transformation lies with them. She believes they must adapt to their new neighbors, but Berenger proposes they regenerate the human race, like Adam and Eve. Daisy has given up hope, calling themselves the abnormal ones; she finds the power of the rhinos seductive, and human love a "weakness." In a series of quick reversals, Berenger slaps her, she recoils and weeps, he apologizes and declares that he'll never surrender and that he'll help her to the end, and she pledges her loyalty to him. The noise of the rhinos becomes more melodious. Berenger calls the sound roaring, while Daisy believes it is singing. He calls her stupid, and Daisy breaks up with him and leaves.