The masked people take Tally to their helicopter and bring her to “the bald head," a hill Shay referred to in the last line of her note. On the way, they explain that they are setting fire to the landscape in order to contain the spread of a destructive weed—the white tiger orchid, biochemically engineered by a bygone rusty to grow heartily, so as to meet a high consumer demand. The flower, though beautiful, has choked all other plant life and is destroying the ecosystem. Tally’s rescuers are rangers—new pretties from another city where people can choose their jobs, instead of being assigned them. They have a friendly relationship with the Smokies, each helping the other out. Waiting on the hill for the Smokies to come to collect her, Tally ponders the betrayal she will soon have to make.
A group of three Smokies—Shay, David, and Croy—find Tally and take her back to the Smoke. Both David and Croy are a few years older than Tally, but only David’s ugliness suits him. Shay, Tally realizes, is in love with David.
The friends are overjoyed to see one another again. Before they arrive at the Smoke, the boys check Tally for trackers and remove one from her hoverboard. They discard the tracker and explain that most uglies arrive carrying one, unbeknownst to them. Tally feels guilty; if only they knew what she is carrying around her neck.
The Smoke is a self-sufficient settlement that simultaneously takes from and gives back to nature. Shay brings Tally to the library there to meet “the Boss,” a forty-something ugly who runs the Smoke. While they wait for him, Shay shows Tally an old magazine from Rusty times, packed full of photographs of historic uglies, what people looked like before the operation existed. Tally is horrified in particular by a photo of an anorexic model in lingerie. This, she reflects, is the price of staying ugly: you want to be pretty so badly you are willing to starve yourself.
At lunch, Tally tells the story of her journey from the city, and receives much admiration from the Smokies. She accompanies Shay on her work assignment after lunch—retrieving scrap metal from old railroad tracks and repurposing it to build new hoverboard paths—and finds joy in working with her hands. She follows David on a metal scouting mission into a partially collapsed tunnel that the railroad cut through a nearby mountain. David confides in Tally about his parents—both middle pretty doctors who escaped the city, founded the Smoke, and reversed their operation. David was born in the wild; he has never lived within the constraints of Tally’s world. For the first time, she understands that if she betrays the Smoke, she will be ruining an entire way of life.
After dinner, Shay takes Tally to the trading post, where she exchanges some packets of dehydrated food for a new sleeping bag and sweater. Shay asks Tally about her necklace: was it a gift from a love interest back home? Seeing Tally’s guilty expression, she presumes that Tally feels bad because she has told this boy about the Smoke, even though she promised Shay she would keep it a secret, and left him instructions in case he wants to join. She forgives Tally for doing so because she did the same thing by telling Tally about the Smoke. The Smokies are still suspicious of Tally, Shay says, because they do not know her, and have to rely on Shay’s word. Tally feels even worse; her betrayal will ruin Shay's reputation.
With time, Tally grows accustomed to the ways of the Smoke. She has yet to reveal its location by activating her necklace. One day, David gifts Tally an old pair of leather gloves he made for himself, so she can protect her blistered hands. While clearing underbrush from a new section of the railroad, Tally discusses her new items with Croy, who is suspicious of Tally’s story. She turned up with too many packets of dehydrated food left for the timing of her journey to make sense. Tally admits she may have exaggerated her perils, hoping that he will believe this new lie. She has lunch with Shay, who seems upset at her. Tally believes this is because Croy has talked to her about his suspicions and almost tells Shay the truth behind her arrival at the Smoke, before she realizes that Shay is actually upset because she has seen David’s gift to Tally. She shows Tally her own blistered hands: same size, but she didn’t get the gloves. It is clear to Shay that David has feelings for Tally, and that Tally hasn’t told him about the boy who gave her the locket back home. She begs Tally to tell him, in hopes that he might give up on Tally and return to Shay. Tally agrees.
David asks to speak with Tally later in the day. Tally responds that she has something she’d like to tell him too. He discloses that he believes Tally came to the Smoke to see if Shay was okay, not because she herself wanted to live there, and he admires her for it. Basking in the glow of his admiration makes Tally feel despicable and undeserving, but the warm feeling he creates in her is not unlike what she feels when she is looking at a pretty. She never knew it was possible to feel that way about someone ugly. Like Shay, Tally has developed feelings for David. David, too, has developed feelings. Maybe the person who gave Tally her necklace will follow her here and she’ll go back to him, he says, but in the meantime, David hopes that Tally will consent to meet his parents.
Az and Maddie warmly welcome Tally into their home, which is built into the side of a mountain a little way away from the Smoke. Tally is shocked to discover the physical similarities between David and his father; where she comes from, parents don’t look like their children, because of the operation. David, who wants to convince Tally to stay in the Smoke, begs his parents to tell Tally the secret that made them run away from the city, the secret about turning pretty.
While serving on the morphological committee, responsible for deciding how the beauty standards of pretties will evolve, Maddy discovered the existence of small lesions in the brains of almost everyone who had had the operation. The only ones who didn’t have these lesions were those with important jobs, jobs that required critical reasoning and quick thinking. In this way, Maddy and Az discovered that the lesions were purposeful, put there by the government during the operation to keep pretties docile. This is why there is no longer war: there is no longer controversial thought. Before word of their findings could spread, Maddy and Az received a visit from Special Circumstances. They were to stop their research immediately and forget what they had seen. Faced with few options, Maddy and Az escaped the city.
They reversed their operations in the wilderness, so that the uglies they recruited to join the settlement would trust them. They have been working to find a cure for the lesions ever since. They know one is possible, because all new pretties have the lesions, but if they go into challenging work, the lesions disappear. Part of their reason for founding the Smoke is to discover what the mental differences are between those who undergo the operation and those who don’t. Only by studying a community of people without lesions can Az and Maddy understand how much of peoples’ sheep-like behavior is due to the lesions and how much is just part of being human.
Walking back, Tally and David discuss what Tally has learned from Az and Maddy. David is surprised to hear that Tally believes it; it takes most people a long time to get accustomed to the idea that their society could be so cruel. Her belief is more confirmation of her difference. To David, Tally is beautiful for this reason, and because she has braved so much to get to the Smoke. Tally is flabbergasted. She has never been called beautiful before.
Is she more beautiful than Shay, she wonders, and then feel immediately ashamed for asking. Yes, David says, she is.
This is an emotional turning point for Tally. She has grown up believing herself to be hideous, spent years being referred to by her ugly nickname—the feature of hers considered to be her "worst." She doesn’t want to be prettier than Shay. She doesn’t want the evolutionary advantage being naturally prettier affords her. It isn’t fair.
David denies that Tally’s physical beauty is what makes him like her, but Tally is doubtful. He sees her body before anything else, and his body responds accordingly—it’s basic science, and it gives her an unjust leg up on Shay. Listening to David, Tally realizes that she would never want him to undergo the operation, because then David would lose what makes him special, he would look like everyone else.
They kiss. But David still doesn’t know the truth of Tally’s locket, and she must find a way to prove to him that she is committed to the Smoke, to staying there with him and being an ugly all her life. Before she can change her mind, Tally throws her locket into the fire, intending to destroy it, so that Dr. Cable can never find the Smoke and David will see that she is loyal to him. The locket incinerated, she is finally free.
The next morning, Tally awakes to a grand commotion in the settlement. Special Circumstances has arrived.
While riding in the helicopter with the rangers, Tally gets a dramatic vision of the dangers of messing with nature. The white-tiger orchids, though delicate and lovely, are choking out all other life in the ecosystem. Their stranglehold on their environment is a metaphor for the total dominion of beauty in Tally’s world. By genetically altering nature’s plan, the scientist who created the orchids—and the government who created the operation that turns everyone into "pretties"—have effectively wiped out any semblance of diversity in, respectively, nature and human nature. As a result, nothing but the orchids, or the city’s singular aesthetic vision, can thrive.
Tally’s exposure to uglies of all ages is initially disturbing to her, but eventually, as their appearances normalize, she wonders if being ugly is really just being at an awkward age, midway between childhood and adulthood, boiling over with puberty’s conflicting messages. The Smokies seem happy. They are true individuals in personality and appearance, totally free to make their own decisions.
Still, the photograph of the anorexic model in the magazine troubles Tally. She does not want anyone to harm their bodies in pursuit of beauty. Ironically, this is exactly what the operation does, and though she doesn’t know it yet, her government is purposefully damaging the brains of its citizens.
Tally continues to be dazzled by the sheer size and majesty of the natural world. While scavenging for scrap metal with Shay, she pauses to look out onto the plains. This moment marks a change in Tally: the most beautiful vista she has ever seen is no longer New Pretty Town: it is here, in the wild.
In the mountain tunnel, David describes the steps his parents took to flee the city and reverse the operation as Tally reflects on the precarious composition of the boulders. One small move, like that made by David’s parents, or the correctly placed boulder, can bring the whole structure down. Similarly, one small move on Tally’s part will affect the lives of everyone around her, should the Smoke be destroyed.
To her surprise, Tally finds that she likes life outside the rules and regulations of the city. She gets joy from doing her own labor, instead of being constantly provided for. That necessities are hard won here makes them all the sweeter. She feels stronger and more self-reliant, which gives her the confidence to be more at peace with the way she looks. The physical beauty of the Smoke has the effect of quieting Tally’s mind. Nature is beautiful as it is, with no alterations. Objects in the Smoke also carry a history. They are not immediately recycled after use, and as such, they feel more dependable and mean more.
When Shay confronts Tally about David’s feelings for her and Tally’s dishonesty about her locket, Tally’s overwhelming guilt returns. She describes the locket as growing heavier around her neck; the weight of her predicament is intensifying. Tally compares herself to a weed, like the orchids. She, too, is only out for her own gain, cutting down everything in her path. But unlike the orchids, she isn’t even beautiful. Reflecting on the fantasy of being pretty with Peris and Shay does not give her the pleasure it once did. It feels flat and rote, meaningless in its conformity.
The revelation of the lesions affecting pretties’ brains rocks Tally’s world. She cannot imagine why her government would do such a thing, until David plants the seed that it is because they are looking to control the masses by dumbing them down, rendering them meek and acquiescent. This, he says, is the real purpose of the operation. Sure, it changes the way you look, but more importantly, it changes the way you think. The pretties have always seemed totally at peace with themselves, but is this the result of maturity or of brain damage? Their selfish, shallow behavior is normalized with the social structure, but just because something is normalized, Tally thinks, doesn’t mean it’s okay.
To Tally, the worst part of the operation is the brain damage, but to David, it’s the damage the operation wreaks on one’s self-esteem. It is awful to live in a world where people are brainwashed into believing they are hideous if they don’t look exactly like everyone else. Tally resolves to destroy the locket once and for all. Incinerating it builds her fire for David, and for her own individuality. Finally, she feels like she belongs.