In Mexico, Augie and Thea stay in the vacation home that belongs to Thea's family, along with a housekeeper, her infant, and the house boy, Jacinto, who eagerly offers them help in training Caligula. Augie begins feeling affectionate towards the lizards, which irritates Thea: "You get human affection mixed up with everything, like a savage." Augie also notices that, in contrast to Lucy, who liked to call him "husband", Thea calls him "lover", like Jimmy's sister Eleanor. One day Jacinto catches an exceptionally large lizard to use as prey, but the lizard bites the eagle in the thigh. Caligula cries out in pain, and refuses to continue catching the beasts. Thea, enraged, condemns the eagle.
Augie begins to sense that though he and Thea love each other, they are "not quite the same in...purpose. She had the idea of action for which love makes you ready and sets you free." Augie, on the other hand, avoids any real commitments. Thea decides to give the eagle one more chance, and brings him to the home of the giant lizards: a steep, rocky, "snaky" place. However, when one of the iguanas bites Caligula on the neck, the eagle cries out and drops the lizard, giving up once again. In a rage, Thea casts stones at the eagle, calling it a coward. Caligula flies back to the house, where food is readily available. Thea begins ignoring the eagle completely, while Augie finds solace in the books strewn about the house. Craving other company, he goes to town in search of excitement: there, he meets the beautiful Stella.
Augie makes a plea on Caligula's behalf, but Thea refuses to listen. Augie takes the matter into his own hands, suggesting that they go back to the home of the giant lizards to determine once and for all whether or not Caligula is capable of doing her job. Augie climbs up the slope on the back of a burro, but descends too quickly, and flies off the animal. He hits a rock, injuring his head. Thea shoots the injured the burro dead and takes Augie back to the house, where a doctor mends the crack in his skull. Thea sends Caligula away to a zoo in Indiana, and nurses Augie back to health. They both mourn the failure of their endeavor, but over time Thea becomes restless and bored. She begins hunting snakes again, and Augie, disturbed, seeks company in the town. He befriends the international vagrant community, and begins playing poker through the night. When Augie suggests that he and Thea marry, she says no.
One day, Augie catches sight of Trotsky standing in front of the church, and thrills at having glimpsed a great man. This sighting makes him think of Einhorn, and Augie suddenly realizes that one of the bodyguards is Sylvester. They greet each other, and Sylvester tells him that Frazer is now one of Trotsky's secretaries. Meanwhile, in town, things heat up for Oliver, Stella's boyfriend; his trouble with the law intensifies, and Stella becomes frightened. Thea suggests that she and Augie leave for Chilpanzingo, and when Augie asks what she has in mind, she tells him that there are supposed to be some interesting animals there. Augie eventually agrees, only to leave her at Oliver's housewarming party to talk with Stella in private. Stella confides to him that Oliver held a gun to her head, and that she needs someone to help her get to Mexico City. She tells Augie that they're in similar situations, trapped by their lovers. Augie agrees, though he shivers "as if my fate had brushed me." Stella's words rings true to him: "you and I are the kind of people other people are always trying to fit into their schemes."
Augie explains to Thea that he intends to help Stella get away from Oliver, but Thea, infuriated, claims that Stella is lying. Augie invites her to come along, but she refuses, and Augie drives away with Stella. He accidentally takes a wrong turn, forcing them to spend the night together. He and Stella sleep together, and in the morning Stella tells Augie that she'll pay him back for his trouble by placing money in a Wells Fargo account for him. She also tells him that he should come by and see her some day. He drops her off in Cuernavaca, where he hires a car for her, and heads back, prepared to lie to Thea. Back at the house, however, Thea refuses to listen to his story; she intuitively knows the truth. She readies herself to go to Chilpanzingo without him, but Augie tries to make up with her. Instead, he only upsets Thea when he complains about her hunting and calls her "fantastic". She responds: "Maybe I am peculiar, that I only know these strange ways of doing something. Instead of sticking to the ordinary way and doing something false." She adds: "I felt mostly alone, as if the world were full of things but empty of people...I must be a little crazy...I'm sorry you're here now. You're not special. You're like everybody else. You get tired easily. I don't want to see you any more." Suddenly, Augie finds himself abandoned once again.
In the throes of a crisis, Augie tries to think of a way to prove to Thea that he loves her: "Everybody gets damaged, and you should forgive me so we can continue." When Augie learns that a former lover of Thea's has gone down to Chilpanzingo, he can only assume the worst, and heads south to profess his love. He confronts Thea, but finds her alone. He asks her whether they can be together again, but she says no. She tells him that she wishes he were dead, and Augie, recognizing that there is no longer anything binding them together, asks one last time whether he can join her on her journey. Once again, however, she tells him that he is not welcome.
When the eagle proves to be a coward, no amount of human effort or discipline can change the animal's essential nature: he is irrevocably "domesticated". The parallel between the eagle and Augie is undeniable. Augie, in the face of Machiavellian influences, refuses to change or to conform to the expectations of others. He shows this by first sympathizing with the lizards that the eagle pursues, and then by sympathizing with the eagle when Thea begins to condemn the creature. Augie exhibits an unflagging desire to prove Thea wrong: first, he attempts to combat her unwillingness to continue working with the eagle, and later, he refuses to allow her to abandon him.
Augie's "opposition", however, proves fatal to the relationship. He opposes Thea by "choosing" Stella, dismissing Thea's assertion that Stella is a liar. This action recalls Augie's decision to choose Mimi over Lucy; he abandons his faithful lover, choosing instead to help Stella escape her dangerous boyfriend. The choice also allows for a degree of passivity: Augie feels that fate has made the decision for him and rushes into the future, closing off the possibility of a life with Thea, just as his decision to rescue Mimi shut off the possibility of him joining the Magnus family. Thea, however, despises all that is dishonest and banal. Already suspicious about Augie's lack of commitment, his decision to come to Stella's aid prompts Thea to make a clean break. In keeping with her forceful character, she rejects Augie as "false" and "ordinary".
The always-adaptable Augie suddenly finds himself abandoned once again. Devastated, he begins to look inward and examine himself: "My real fault was that I couldn't stay with my purest feelings." Thea's abandonment echoes Augie's unknown father, who swept through the house like a "god" and impregnated his mother before deserting them. The narrative signals that Thea's influence might have actually done Augie some good. In acting always in his "opposition", however, he destroys the chance to discover what might have been.
Augie meditates: "What was the matter that pureness of feeling couldn't be kept up? I see I met those writers in the big book of utopias at a peculiar time. In those utopias, set up by hopes and art, how could you overlook the part of nature or be sure you could keep the feelings up?" In other words, can something as pure as "love" become the material upon which one builds a future? A material world based on love - or "utopia" - starkly contrasts with the world of the Machiavellians, where the individual confronts his or her circumstances strategically, in an effort to accumulate power. Thea is the one figure in the novel who attempts to strike a balance, mixing her "love" with her "will".
Augie states in a memorable passage: "Everyone tries to create a world he can live in, and what he can't use he often can't see. But the real world is already created, and if your fabrication doesn't correspond, then even if you feel noble and insist on there being something better than what most people call reality, that better something needn't try to exceed what, in its actuality, since we know it so little, may be very surprising. If a happy state of things, surprising; if miserable and tragic, no worse than what we invent." The fundamental problem that can be derived from this passage is that the two lovers have different visions about what constitutes a "good" life. While they both believe that "love" is the fundamental building block, they have differing perspectives on how to build upon this love. Usually, individuals in a relationship must compromise, but Thea shows no inclination to do so. From Augie's perspective, he is nothing more than a "recruit": "There's one image that gets out in front to lead the rest and can impose its claim to being genuine with more force than others, or one voice enlarged to thunder is heard above the others. Then a huge invention, which is the invention maybe of the world itself, and of nature, becomes the actual world - with cities, factories, public buildings, railroads, armies, dams, prisons, and movies - becomes the reality. That's the struggle of humanity, to recruit others to your version of what's real. Then even the flowers and the moss on the stones become the moss and the flowers of a version." The "pure feeling" of "love" fails to dominate the need for control and power, and the lack of freedom only fuels any attempt to escape control. This misunderstanding causes love itself to be cast to the side. Augie is astonished at the dissolution of his affair, because he had put such great store in love. Suddenly, he feels "ugly", and wonders what to do next. Having freed himself up to the possibility of pursuing love, he recognizes that he has failed to commit to that love and do whatever it takes to ensure its survival. This forces Augie to consider ways in which he might be able to grow and change.
The contrast between Stella and Thea is underscored by Augie's choice of the former over the latter. Thea, always honest, tells the truth about Augie, as well as about Stella. Stella, however, proves to be less-than-truthful. The story about Oliver holding a gun to her echoes Einhorn's warning about Joe Gorman, but the key difference lies in the intention of the storytellers. Both assertions may have been false, but Einhorn hoped to set Augie upon a better path, while Stella is concerned only with herself, unmindful of the detrimental effects a romantic liaison might have on Augie's relationship with Thea.
Since Stella becomes a part of Augie's "fate" and "future", he experiences the human bitterness Kayo Obermark described with regard to Mimi's abortion: "It might be in the end that the chosen thing itself is bitterness, because to arrive at the chosen thing needs courage, because it's intense, and intensity is what the feeble humanity of us can't take for long." Though Augie "passively" makes his choice, he lives with the consequences with "courage" and tries to endure the bitterness that always comes with the thought of what might have been.