Hundreds of years ago, humanity exhausted Earth’s natural resources, causing society to descend into chaos and war. The best scientists in the world took the mission of saving what was left of civilization and created genetically modified orchids that became the new energy source. However humans still fought over their differences, so the scientists also created “The Transformation”.
When they turn sixteen, every person goes through a life-changing operation that transforms them into their most perfect self. These people are known as “Pretties” and since they’re perfect and happy living in the City, conflict is avoided. Those who haven’t gone through the procedure yet are called “Uglies” and stay in the dorms in Uglyville.
Tally can’t wait to become a Pretty and constantly uses an app on the mirror to see her how she’d look after the procedure. Her best friend is Peris and they call each other “Nose” and “Squint” since childhood. Sometimes they go to the bridge during curfew hours and use special glasses to watch the Pretties partying in the city.
Tally will be turning sixteen in three months but Peris is older and he’s getting his operation tomorrow. They have matching scars on their hands and promise they won’t let the doctors erase them when they become Pretty. At that moment a patrol drone flies by so they run back to their dorms.
The next day during assembly, Tally overhears other students discussing “The Smoke”, a hidden place outside the city led by some guy named David. It’s said many people escape the City and hide there, but most students don’t think it’s real. At that moment a hologram of Governor Cable appears and gives a speech on the importance of being pretty and perfect.
Then all those who turned sixteen are called and Tally says goodbye to Peris while telling him to meet her at the bridge in one month. In the evening, Tally watches the fireworks above the city and remembers the day she met Peris. Her parents had just dropped her at the Dormitories and Peris was behind her in line.
They exchanged nicknames and hit it off, so they quickly became best friends. One day Peris accidentally cut his hand when taking a tablet from Tally, so she got the same scar while they promised to stay friends forever. Days pass and Tally sticks to her routine of going to class and looking at herself in the mirror.
She often checks her interface ring too, but there are no messages from Peris. After a month, Tally uses her ring to hack the window open and leaves it behind because it has a tracker. She sneaks around and makes it to the bridge, but Peris hasn’t shown up.
Getting worried, she uses some rope to climb on the bridge and dangerously moves under it until she makes it to the City. She sneaks around by hiding behind the plants, but when a partygoer drops a mask, Tally grabs it and puts it on. The mask puts on a hologram on her body, making it look like she’s wearing a fancy dress.
Now Tally can get into the party, and she’s amazed by tall the decorations. Eventually she finds Peris, who looks completely different and doesn’t recognize her. Tally takes off her mask and asks why he didn’t go to the bridge, so Peris explains things are different now and he doesn’t know how he could relate to her anymore.
Tally can’t believe what she’s hearing and realizes how much he’s truly changed when she notices his scar is gone. At that moment the security system detects her presence and Tally has to run away from the incoming guards. She gets stuck in a balcony, so she steals a bungee jacket and jumps.
The fall is rather long but the jacket causes her to bounce and land gently nearby instead. Then Tally runs out of the city by climbing under the bridge again. When she accidentally kicks a stone into the water, a drone finds her and comes closer to arrest her.
Suddenly her classmate Shay appears and makes Tally get on her hoverboard so they can fly away to escape. The drone tries following them, but Shay is a fast driver and manages to lose it by doing tons of crazy turns in the woods. To thank her for the help, Tally breaks into the kitchen and steals some snacks.
The girls bond over their experiences and how hard it is to be left behind when all their friends turned sixteen first. They realize they have the same birthday and get excited to have a friend to become Pretty with. The next day Shay brings a second hoverboard and tries teaching Tally how to use it, but she immediately falls.
At school Tally is shocked to see some girls give Shay back a book since those aren’t around anymore. The girls are impressed by the text’s description of surviving in nature and wonder if that’s what the Smoke is like. Tally borrows the book while the girls call her cool for her stunt last night, which makes her angry because it means Shay told everyone.
She’s afraid they may punish her by denying her the operation, but Shay assures her the system wants everyone to be a Pretty. As days pass, Tally reads the book but she still keeps dreaming about the operation. Shay continues to teach her how to use the hoverboard and in return Tally keeps on hacking with her ring to get extra food.
Tally also shows Shay her Pretty designs on the app, but Shay doesn’t have an account. In fact she isn’t excited about the operation at all. Eventually Tally learns how to fly well and the girls use their hoverboards on crazy ramps to have fun.
When Tally gives Shay the book back, she says she wishes she could visit that beautiful nature and Shay mentions that it wouldn’t be so bad not to get the operation, but Tally thinks that’s crazy talk. Suddenly Shay mentions The Smoke and takes Tally to the edge of the woods. After leaving their rings on some branches, they cross the border by riding their hoverboards over the river.
Eventually they make it to the ruins of an old city and Shay tells Tally about ancient objects like rollercoasters. Next Shay takes Tally into an abandoned building and drops the truth: The Smoke is real and David will be arriving soon. Shay refuses to get the surgery and will be leaving tonight, so she wants Tally to come with her.
However Tally turns her down, saying she doesn’t want to be free she wants to be Pretty. An upset Shay gives her directions to reach The Smoke in case Tally ever changes her mind and hugs her before leaving on her hoverboard, following the sign of David’s fire in another building. The next day it’s Tally’s birthday so she goes to the clinic for the surgery.
However they call everyone except for her. Then a guard takes her away in an aircraft to see Doctor Cable, who explains Shay is missing. Tally says she doesn’t know anything, but Cable can see her vitals on a screen that indicate she’s lying.
Cable tells Tally that Shay is in danger because David brainwashed her, and he’s known for holding people against their will. When Tally insists she doesn’t know anything, Cable sends her back to her dorm without getting the surgery. That night, Tally hears a noise and is surprised to see Peris appearing at the window.
Tally explains what happened and Peris thinks she should tell Cable what she knows so they can finally be together. The next day Tally is again taken to see Cable, who tells her David is developing a weapon to attack the City so she needs Tally to infiltrate The Smoke. Tally agrees to help and Cable promises that if she’s successful, she’ll get the surgery.
She also gives Tally a necklace that flashes in her eyes, which she must activate when she finds the weapon’s location. Afterward Tally follows Shay’s instructions and rides the hoverboard on the old roller coaster for a few miles. Eventually she finds a gap and falls in the woods, but she’s caught by a force field.
There she finds abandoned train tracks, which she must follow to find The Smoke. For the next few days Tally survives in the wild like she read in the book and admires nature like never before, she also gets to climb a mountain. The train tracks have a big gap in the middle of a chasm, so she gets on the hoverboard again and makes a big jump that shuts down the board.
Tally starts falling very fast but before she hits the ground, the hoverboard reactivates and she reaches the other side of the chasm. Now she has to wait in a field of flowers like the instructions said. Meanwhile Cable brings Peris to her office, revealing he went to her dorm the other night because she asked him to.
Peris admits it felt good to be in town, as if he could think clearly again. Then Cable announces a select few have been chosen for a new procedure and Peris agrees to enter the surgery machine to get body enhancements. That night Tally wakes up coughing because of smoke.
She discovers the field is on fire and doesn’t know what to do, but suddenly a mysterious person picks her up and takes her away. This is David, who starts scanning Tally and her things for trackers. He finds one inside the hoverboard and removes it, but his scanner doesn’t react to the necklace.
At the same time Cable’s men receive an alert about the tracker being removed and she sends people to search the area. In the morning, David and Tally make it to a Smoke outpost, where Tally gets to reunite with her friend. Shay is super excited to see her, but Croy is suspicious.
The group camps for the night and Shay asks about the necklace, so Tally pretends it was a gift from Peris. Tally is surprised to see Shay happy after what Cable said and tries to express her worries, which makes Shay think she came to convince her to go back. An argument ensues and Tally agrees to give the Smoke a chance.
The next day Tally learns that the Smoke stars fires on purpose to burn the orchids because they’re actually toxic and destroy any place they’re planted in. Tally doesn’t believe him and says the orchids were the clean energy solution, but David explains that’s a government lie and that the flowers are turning the planet into a wasteland. He wants to take Tally on their mission to prove it and Croy protests, but Shay vouches for her.
The group has an old helicopter that they fixed with solar panels and they go on a flight. Now Tally can see the area where orchids used to grow, which is nothing but desert. Using a flamethrower, Shay burns down as many orchids as possible.
At that moment Croy’s tablet detects someone coming so David lowers the helicopter to hide in the smoke. The movement looses the rope holding Shay and she falls. Cable's scouts sent are getting closer, so Tally ties a bag at the end of the rope for weight and throws it off before using it to go down.
The helicopter starts to lose lift while Tally looks for Shay among the flames. Luckily she finds her and when a scout tries to get closer, Tally grabs the bag on fire and throws it at him. Then the girls hold onto the rope and the helicopter flies away right before a scout can jump on too.
After the group lands, Croy points out the scouts could’ve only found them because of Tally, but Shay defends her and David thinks anyone who risks their lives for a Smoke is worthy of a chance. The group camps for the night but Tally can’t sleep because she keeps thinking of Cable and how she taught her to manipulate the rebels. She leaves the tent for a walk and finds David bathing in the river, so she gets back in the tent to hide her embarrassment.
The following day Tally is blindfolded and finally taken to the Smoke, where a whole community is thriving in nature. Tally thinks it’s harder than in the city, but she admits food tastes better when you grow it yourself. Even old people must work and there’s no money, so things are shared or traded.
Most importantly everyone is there by choice. The train tracks are being recycled to make tools but they make no weapons because they’re pacifists. One afternoon Tally finds a weird door and tries looking inside but Croy catches her red-handed and sends her away.
Tally starts using tools to help with the tracks, tastes spicy food for the first time, and shares the dances around the fire. Sometime later David teaches Tally how to use a hunting crossbow and they enjoy their time together. It takes her a few tries but eventually she hits the practice target.
On their way back, David explains he never saw the City because he was born in the wild and grew up with his family. Tally is shocked to hear this because she barely knew her own parents. Then David gifts her a pair of gloves.
At that moment a Smoke member comes back from orchid burning with a wound, saying the scouts are still around. She also explains those scouts were faster and stronger than normal. Afterward Shay notices Tally wearing the gloves and points out it’s a big deal.
Objects have different value there and David made those, so giving them to Tally means he likes her. Shay tells Tally to make her choice already and stop playing with them. The next time Tally goes on a walk with David, she mentions she heard rumors of a weapon to destroy the city, so David takes her to a house far from camp.
There she meets David’s parents Az and Maddy, who are the ones guarding all the books. They used to be cosmetic surgeons for the government and got suspicious of a few tests, so they started to investigate. It turns out the physical changes were just a cover to hide the fact people got their brain altered too.
Becoming a Pretty means being dumb and slow under a fake sense of happiness so the state could easily keep them under control. The operation has also killed many people, which was kept secret. When Cable realized Az and Maddy knew the truth, she stole all their research.
People working for the state like doctors were actually given a cure so they could think clearly while working, so David’s parents chose to flee the city and grow old normally in the woods. They’ve been looking for a way to recreate the cure, but there’s a synthetic component they don’t have so they only have a base serum. This is the so-called weapon that could destroy the city.
After the meeting is over, Tally throws her necklace into the fire, choosing to stay with The Smoke. She also tries telling David that she’s done terrible things, but he doesn’t care because she’s a new person now, then they share a kiss. In the fire, the necklace sparks.
In the morning, City aircraft arrive at The Smoke and open fire. Everyone starts running away and the scouts chase after them, only to fall for the traps already in place like nets and logs. Unfortunately they’re too fast and strong so traps aren’t enough to stop them.
Soon they’re knocking down and capturing every rebel on their way, including Shay. Tally manages to find a hiding spot with David, who wants to go out to help. However she stops him since they’re too strong for him.
The duo sneaks to the spot where they’re gathering all the prisoners and Tally is devastated to discover Peris has become a scout. Az and Maddy are captured at the same time Cable arrives and demands to know where David is. The parents refuse to talk, so Cable orders Peris to kill Az.
David and Tally run out to stop him, but it’s too late. Then Cable tells everyone that Tally has been working for her and now the Smoke members hate her. While everyone is distracted, Maddy hides the serum in David’s pocket.
As Cable announces everyone will receive the surgery, Tally runs to the supply shack and starts a fire. She also grabs a crossbow and escapes through the window while a scout tries to break in. Suddenly the fire causes an explosion and it throws the scout back, it also allows David to run away.
A scout comes after him, however Tally stops him with an arrow. Peris wants to join the chase, but Cable anounces they're leaving. Some scouts destroy Maddy’s research and set the area on fire while the others push all the prisoners into the aircraft.
After they’re gone, David gathers the few supplies he can find for a rescue mission. Tally tries approaching him and he attacks her with a knife, barely stopping himself from hurting her. She wants to help him to rescue the others and he points out he doesn’t trust her anymore, so Tally explains he needs her because he’s never been to the City.
Sometime later in the City, Tally approaches the students that read Shay’s book and introduces them to David to prove that The Smoke is real. Tally borrows an interface ring from them and asks them to gather lots of kids to create a distraction. Soon a bunch of teenagers write “The Smoke lives” in the sky using their hoverboards.
Meanwhile David and Tally wait for the aircraft to leave the clinic and get inside using hoverboards too. They go through the aircraft tunnel and land safely thanks to the bungee vests. They carefully sneak around and Tally uses the ring to hack a lock, but this isn’t just a kitchen and it doesn’t work.
Suddenly the door is opened by a Pretty and David immediately starts fighting him. They exchange a few hits before David overpowers him and holds him against the wall, so Tally takes his ring. Then David throws him in the corridor and Tally locks the door.
As the alarms go off, the duo finds the cell and uses the ring to free everyone. Tally realizes Shay isn’t around and Croy reveals she was already given the surgery. While most of the group escapes, David, Tally, and Maddy go looking for Shay, but when they make it to the lab it’s too late: she’s already a Pretty.
Tally cries and apologizes, yet Shay swears she loves it. At that moment Cable and Peris arrive and force the trio to get into the machines so they can finally get the surgery. The process begins but before the needles can start cutting, the Smoke’s helicopter appears outside and Croy opens fire with the flamethrower.
Cable and Peris are forced to run and the machines get damaged, so the system fails and the operation stops. The trio comes out and Tally grabs Shay while Maddy gets the component she needed from a cupboard. The group runs to the roof and finds Peris, so Tally tries to make him see reason by using their nicknames and pointing out a piece of glass gave him his scar again.
Peris gently touches Tally’s face and David thinks it's an attack, so he tackles Peris and tries to fight him. Peris is too strong and keeps beating him up, but before he can kill him Tally uses a hoverboard to move fast and tackles Peris, making him fall off the edge. He holds on for a second and says her nickname before he falls into a waterfall.
Afterward the group escapes on hoverboards and see the other teens making the drones crash against each other in the sky. They hide in the abandoned city and Maddy takes the serum from David’s pocket to finish mixing the cure. However she can’t be sure if it’ll actually work or have bad side effects for the brain.
Shay doesn’t want to take it and Shay refuses to force it on anyone, so Tally volunteers to be the test subject. She’ll hand herself in and let them do the surgery so she can then take the cure, promising to keep a sign for them to know if it works. The aircraft and Cable are coming, so after a final goodbye, the group runs away while Tally lets the scouts arrest her.
Sometime later Tally is the perfect Pretty living in a very fancy apartment. She swears she loves being like this, but the scar on her hand reveals she’s still herself and lying as a spy.