Plot

A world in which a compulsory operation wipes out physical differences and makes everyone pretty.

In a future post scarcity dystopian world in which everyone is considered an "ugly," but then turned "Pretty" by extreme cosmetic surgery when they reach the age of 16. It tells the story of teenager Tally Youngblood who rebels against society's enforced conformity.—lsidney-419-843438

In the future, the world has fallen into chaos after exhausting all natural resources. The people of the previous age are known as Rusties. To keep humanity alive, scientists first create genetically modified orchids that are a new energy source, and second, a surgical procedure to make people pretty; this way, everyone's perfection will not cause any further chaos. The surgery was supposed to control human nature by eliminating differences and creating a more homogeneous society. The surgery is performed on "Uglies" when they are 16, before allowing them to the city where celebration occurs as the "Pretties". The Uglies live in an isolated part of the city in their dormitories, which they enter as kids, and only graduate at the age of 16. The Uglies are only allowed into the main city after the surgery.

Tally (Joey King) and her best friend Peris (Chase Stokes) are Uglies, but Peris being three months older, leaves for his surgery first. Peris had feelings for Tally, but he could never express them to her to her face. The two share scars on their hands which they vow to keep despite the Pretty procedure. They also promise to remain friends and meet again after their procedures. Tally texts Peris multiple times over a month but gets no response. They had promised to meet each other at the bridge connecting the dormitories to the main city on a specific date. Tally waited, but Peris never showed up.

Tally, anxious to see Peris again, sneaks into the city. She is shocked by his appearance, and his different personality. The scar they vowed to keep is gone. When Tally is discovered, she is chased by the Wardens back to the Uglies' dormitories. Tally was trapped on the bridge but is rescued by a fellow student from the dormitory. Later, she befriends Shay (Brianne Tju), a rebellious Ugly who tells her about "The Smoke," a land of freedom in tune with nature. Shay and Tally have the same birthday. Shay teaches Tally how to ride a hover-board.

Shay encourages Tally to join her, reject the surgery, seek out The Smoke and its leader David (Keith Powers). Shay had taken Tally to the abandoned ruins of the old world and says that The Smoke is 4 days away. Shay had brought food supplied with her from the dormitories. Tally refuses as she says that she only wants to be Pretty. Shay gives tally directions to the Smoke, in a coded language that only Tally would understand, and leaves.

On her 16th birthday, Tally is denied her procedure until she tells Dr. Cable (Laverne Cox), the leader of the operations, where Shay is. She is told that David is dangerous, will hurt Shay, and that he is also building a weapon to attack the Pretties. Tally is sent back to the Dormitories to think it over. At night she is visited by Peris who tries to persuade her to cooperate with the authorities. Cable gives Tally a tracking device in the form of a necklace that she can wear around her neck. Tally is sent as a spy into The Smoke. She follows the instructions given by Shay and travels deep into the forests. Tally reaches the Smoke, reunites with Shay, and meets David. David finds a tracker on Tally's hover-board and cannot detect the tracker in her necklace. Meanwhile, Dr Cable makes Peris undergo an enhanced procedure.

David's colleagues include Croy (Jan Luis Castellanos). David and his colleagues set fire to the orchids powering the cities as he says that the orchids suck all the nutrients from the soil and destroy everything in their path. David says that the orchids are turning the planet into a wasteland. Tally sees this with her own eyes. While setting an orchid field on fire, Shay falls from the helicopter and Tally goes into the fire to rescue her from 2 scouts who were running towards Shay. David manages to pull them out of the fire just in time. Croy is perplexed how the scouts found them so soon after Tally arrived. David gives credit to Tally for saving Shay and believes in her. David takes Tally to The Smoke.

David was born and raised in the Smoke by his parents, while Tally's parents left her at the dormitory and promised to look her up after her surgery. Meanwhile, the scouts are getting closer, and they are stronger and faster than the normal Pretties encountered before. Shay wants Tally to make a choice and says that she cannot have one foot in the Smoke and one in the city all the time. As she begins to grow close with David, he and his family reveal the truth about the surgeries: they limit human brain capacity, so the Pretties are easily controlled. A select few are given a cure to become the scientists surrounding the whole scheme. David's parents worked as some of those scientists until they discovered the truth and fled.

Ever since, they have been working to develop the cure themselves. This is the weapon that Dr Cable had mentioned. They have created the base serum, but they need a synthetic component to complete it. Tally also learns the orchid energy source is toxic to nature and that is why The Smoke rebels set them on fire, to wipe them out. Tally and David share a moment together, and she tosses her tracker into the fire after renouncing the system and rejecting her chance to become a Pretty.

Her tracker is still active and signals Dr. Cable, who arrives with scouts to round up the rebels. Peris, who was modified to be a near-invincible soldier, kills David's father, and discovers Tally has turned traitor. Tally and David manage to escape. Tally convinces David to take her with him to free the captured rebels. Tally says that she was told that David would hurt Shay and so she came to rescue her. She tried to destroy the pendant and instead it called her. Tally says that she has been to the buildings were the Uglies have been kept hostage.

Upon arrival, everyone is freed except Shay, who already underwent her procedure. Completely changed and oblivious to her previous cause, she is taken with the rebels to a safe spot after David's mother steals the final piece to her cure. Peris stands in their spot and David attacks him. Tally has no choice but to help David and in the process Peris is killed. Yet, David's mother does not want to administer it on Shay as she's unwilling.

Tally volunteers to undergo the surgery and test the cure. She swears she will not let being Pretty change her drive for justice. She bids David and her friends goodbye.

A Pretty Tally lives in the city, but implies she kept her promise to the rebels, as we see her childhood scar remains.