Pretties by Scott Westerfeld is the second book in the Uglies series. In this novel, Tally is now a pretty living in New Pretty Town. While attending a party, she is approached by an ugly whom she vaguely recalls from her time in the Smoke. This ugly tells Tally that he has a package for her, but he leaves it hidden, forcing her to work to find it. With the help of Zane, a friend and leader of the clique, the Crims, Tally is able to clear her mind enough to find the package. There is a letter inside the package from Tally, written when she was an ugly, telling her that the pills included inside the package are a cure for lesions put on her brain during the "pretty" surgery. Zane convinces Tally to take the cure, agreeing to share it with her. When Tally's head begins to clear, she begins to recall why she had decided to remain in the Smoke months before and begins to plot an escape from the city with Zane and the other Crims. Pretties is the exciting sequel to Uglies, a story that not only questions vanity and shallow behaviors, but questions the basic conformities of society.

Tally is dressing for a party in the middle of the afternoon and feels still hung over from a party the night before. Shay comes to her room with breakfast and shows off new surg she has recently had performed. Peris and Fausto arrive, showing off their costumes for the party and talking about the vote that is to take place that night, inducting Tally into the clique, the Crims. At the party, Tally sees someone dressed up as though an agent for Special Circumstances, an idea that frightens her as much as it confuses her, because few pretties even know about Special Circumstances. Eventually Tally confronts this party goer and discovers that it is an ugly she vaguely remembers from her past life as an ugly, Croy. Croy tells Tally he has a package for her, but before he can hand it over, they can hear footsteps on the stairs.

Tally rushes back outside and sees that Croy has jumped off the side of the party tower. Tally grabs Peris, who is wearing a bungee jacket, and jumps after Croy. When she lands, Peris hits her in the head with his knee as the bungee jacket takes him back into the air. The shock of the injury clears Tally's head enough that she begins to remember more about Croy and her life in the Smoke. Tally chases down Croy and he tells her he has a package for her that he will leave in one of the mansions of New Pretty Town.

The following day, Tally's head is once again pretty. Tally only recalls her adventures with Croy and what he told her when Zane kisses her. With Zane's help, Tally remembers more about Croy and together she and Zane go to the building where Croy said he left the package. However, it proves to be difficult to find the package, forcing Tally to become more and more bubbly to figure out the clues. Finally, Tally and Zane realize they must climb a tower to find a key that will unlock the package. When they finally get the package, they discover a letter written by Tally with Shay's help when she was still an ugly. The letter tells Tally that the pretty surgery has placed lesions on her brain and that there is a cure, one that Tally herself promised to be the first test subject for. However, the idea that the cure might cause permenant brain damage causes to Tally to hesitate. When Zane and Tally hear Special Circumstances coming after them, they decide they must take the pills, so each takes one.

The cure appears to work for both Zane and Tally, but Zane begins to have debilitating headaches. Tally decides his only hope is if they can get him to the New Smoke where Maddy, the cure's inventor and a doctor, can help him. Tally and Zane stage an escape from the city, but are separated. It takes Tally several weeks to make her way to the Rusty Ruins where she meets up with David. When they reach the New Smoke camp, Tally learns that the cure was meant to be taken in two pills and that Zane got the pill with the nanobots that were designed to destroy the lesions, but that Tally took the pill that stops the nanobots. For this reason, the nanobots continued to work in Zane's brain, causing brain damage.

Before Tally is in the camp for more than a few hours, a signal begins to go off, alerting Special Circumstances to their location. They discover that the signal is coming from a tracker in Zane's mouth that is wired to both a tooth and his jaw. Zane cannot escape with the others. For this reason, Tally decides to remain behind. When Special Circumstances arrives, Tally discovers that Shay has become a Special. Tally is then knocked unconscious and turned Special, too.