Hamm tells Clov to check the earth outside the window with the "glass" (the telescope). After making two trips for the stepladder and telescope, and viewing the audience, Clov checks and reports: "Zero." Hamm reflects, "Nothing stirs." Clov looks into the ocean and sees that the lighthouse is now completely sunken, the horizon is barren of gulls, and the waves are still. The sun is "zero," even though it is not yet night, and gray light blankets everything. Clov asks why they go through the farce everyday, and Hamm answers that it is routine. He then says that he saw a sore inside his breast last night. Clov thinks it was his heart, but Hamm insists it was "living." Hamm then wonders if he and Clov are beginning to "mean something"; Clov scoffs at this notion. Hamm is taken with the idea, and imagines that if someone observed them for long enough he might get ideas, and that they, too, might be verging on something meaningful. He is interrupted when Clov scratches a flea on his body. Hamm is astounded that there are still fleas, and begs Clov to kill it, as "humanity might start from there all over again!" Clov goes and gets some insecticide, which he sprinkles inside his pants. He thinks he has gotten the flea, although he and Hamm debate the verbs "laying" and "lying."
Hamm pees, then zealously proposes that he and Clov leave for the South, "to other mammals!" Clov declines, and Hamm says he'll do it alone and tells Clov to build a raft. Clov says he'll start, but Hamm stops him and asks if it's time for his painkiller—it's not—and inquires about Clov's ailing body. Hamm reminds Clov that one day he'll be blind, like he is, and that he'll be alone, surrounded by infinite emptiness. Clov says it's not a certainty, and asks if they all want him to leave. Hamm says yes, and Clov says he'll leave. Hamm says Clov can't leave them, so Clov says he won't. Hamm asks why Clov doesn't "finish" them—he'll give him the combination to the larder—but Clov says he couldn't do it, and will leave.
Hamm asks him if he remembers when he came here, but Clov says he was too small. Hamm asks if Clov remembers his father, but Clov doesn't remember for the same reason, and says Hamm has asked him these questions millions of times. Hamm says that he was a father to Clov, and his house was a home for him—statements that Clov agrees with—but that he himself had no father, no home. Before Clov can leave, Hamm stops him again and says that there may be greenery beyond the hole they're in, and asks Clov if his dog is ready. Clov returns with a three-legged toy dog, which he gives to Hamm. Hamm wants Clov to see if the dog can stand, but he can't. Clov says he is and holds it upright so Hamm can pet it. Before Clov can go, Hamm asks if he has had his "visions," and they discuss an old woman named Mother Pegg. Hamm tells Clov to get him his gaff (a large iron hook), and Clov wonders out loud why he never refuses his orders. He gets it for Hamm, who unsuccessfully tries to move his chair around with it.
After they fight about Clov's retrieving the oilcan for the chair's wheels, Hamm recollects a madman painter-engraver friend of his who thought the end of the world had come, seeing ashes instead of nature, and that "He alone had been spared." Clov asks when that was, and Hamm says a long time ago. Hamm asks how he'll know if Clov has left. Clov says if he whistles and he doesn't come, then he's left. Hamm is not convinced—Clov might just be dead in his kitchen. He orders Clov to come up with an idea, and after some pacing on his bad legs, Clov decides he'll set his alarm clock, and if it doesn't ring, it means he's dead. He retrieves the clock and tests the alarm. Hamm says it's time for his story, but Clov doesn't want to hear it. Hamm tells him to wake his father, and Clov looks into the ashbin of the sleeping Nagg.
While it is purposely unclear exactly what has happened in Hamm's vacant world, it is obvious that not only is he living in his own personal endgame, but in some kind of physical "endgame," a post-apocalyptic landscape in which he and the others are the sole inhabitants—everyone else has been "finished," to use his vocabulary for death (in fact, his frequent references to his home as a "shelter" evokes a postwar shield from nuclear radiation). His misanthropy is so great that he fears the rebirth of humanity, evidenced by his anxiety over the flea. This anxiety takes off from an idea explored at the start of the play, that existence is cyclical—that the ending is the beginning is the ending. When Hamm suggests they leave, it is a futile effort; in this cyclical world, there can be no such things as "leaving" or "arriving," as one always ends up back in the same place—note Clov's frustrating inability to leave the room in this section (no wonder he prefers the sound at the end of the alarm, while Hamm likes the middle).
Ham was the son of Noah in the Bible, and Noah's story, of course, is one of regeneration, of an ending that yields to a beginning. The allusion is ironic, and Hamm's father in Endgame, we learn, is Nagg; Hamm is a surrogate father to Clov, so the three generations are all infirm, near the end of their lives, and no new beginnings will issue from them. Whatever path Hamm's life takes, it will be less of an arc and more of a circle; and since even a dot is a circle, then his static position in the center of his room can itself be considered a cyclical journey. Healthier, in Hamm's opinion, is to be like his engraver friend (whom some critics compare to English Romantic poet William Blake) and see everything as already finished. At least the engraver can make some meaning out of the world, as he works with a finished product; in Hamm's circular existence, he never has the closure necessary to make a final statement. This is why he feels it is "beginning" to mean something; each day he starts to see significance, but because of the endless repetitions, he can never finish ascribing meaning. Clov's definition of routine as a "farce" (something Nell also says) makes it evident that, in Beckett's view, only absurdity can result from repetition, not significance.
There are several allusions to Dante's Inferno which solidify the idea of circularity. They're in a hole, and Hamm has previously mentioned the "other hell" beyond the wall. The Inferno also worked on a circular system; its nine descending circles of Hell promoted the idea that those inside would be doomed to repeat their misery for all eternity, and the whole work was based on motifs of halves, of being stuck in the middle of something. The light in Endgame has a similar purpose; neither light nor dark, it is gray, a medium shade without a definite beginning or end. It also underlines Clov's difficult position between staying and leaving. Light seems to be a symbol of hope to him (he stares at his light dying in his kitchen, and he is dismayed when he sees the lighthouse is completely sunken), but since it is half-light, he retains only enough hope to desire leaving and not enough to make himself leave.