Central Park on a beautiful day. Birds fly over Sheep Meadow. Fish gargle away like speechless sports commentators, as the bravest of them play a sort of game with the catch-and-release fishing lines. And at the center of this world, beloved, upper-class squirrels enjoy a nice day in the park, being fed by friendly humans at a picnic. The bustle of so many squirrels around their CENTRAL TREE mirrors the human bustle on the streets of New York. JULIE, 6, is introduced to her future kingdom, which she hopes to take over when her dad, MAYOR ELRICH, retires one day. A group of Found Children (orphans, mostly chipmunks) holds hands and walks with their teacher. Elrich greets the teacher. It’s a perfect day.

The peace is suddenly shattered, as a group of rats pull off a heist at the picnic, causing a panic. Security Squirrels spring into action all over the park. Julie is covered in picnic items that make her look like a rat. Suddenly, the humans turn on her, and she’s saved by a sweet little rat - ROME, 4. He tells her that he was supposed to steal her earrings during the heist - his initiation into being a real rat - but he doesn’t want to steal. Julie sees his innocence and wonders why rats and squirrels are treated so differently. She gives him one of her earrings as a gift and shows him how it glitters in the light to get him to stop crying. Rome runs away, this time to avoid being seen by the squirrels, as Julie’s parents come back for her.

Bothered by her encounter, Julie asks her father why rats are treated differently. After all, she found pictures of rats and squirrels living together behind the old bathroom tiles at school. The next day, the school is moved to a new branch of Central Tree, and the bathroom is sealed off.

10 YEARS LATER… Julie, now properly indoctrinated as an upper class squirrel, is given a seat at the council, in order to begin her training to become the mayor one day.

It’s a huge honor and a rare exception at her age. She is delighted, but she knows that she’ll have to prove herself. This position is far from guaranteed.

Her first assignment is to patrol a certain part of the park at night, supervised, of course, in order to prepare her for her first security council meeting. During the mission, they happen upon an illegal rat operation. The group breaks up in the skirmish, and Julie is abandoned. Her clothing gets snagged on a passing biker, and before she knows it, she’s faaaar from home.

Alone, in the dark, in enemy territory, she’s terrified. Some nasty rats realize what’s going on, and move in on her. A young rat swoops in and saves her. It’s Rome, but they don’t recognize each other. He offers to take her back to Central Tree, but in order to get there, she has to go on a brief adventure, past all of the things she’s always wanted to see and do but was never allowed to.

They cross Central Park Lake on a rowboat, ride under a horse and carriage, eavesdrop on people at the whispering bench, and watch a movie from a secret lookout Rome built on the roof of the Met. He found this place once, when a couple of human kids took him around Central Park for the day. That experience changed the way he sees humans forever, but none of the other rats understand.

From up here, Central Park is beautiful and clearly meant for more than just squirrels. It’s amazing. And Rome is amazing, and… sophisticated. Julie invites him to meet up tomorrow, but he can’t. Rats can’t go out in the day because of the danger and the squirrel-imposed curfew. In fact, all the things Rome’s always wanted - like oreos - will have to wait, though, because rats never get anything good. As Rome turns to leave her at her door, his collar shifts, and Julie sees her old earring, now a necklace around Rome’s neck, glitter in the light. And just like that… she’s smitten.

Julie puts on makeup and wraps her tail to look like a rat. She’s already jerry-rigged the window security system and propped it open. Suddenly, there’s a knock at the door. It’s her dad! The security council meeting has started, and she’s not there. “That was tonight?!” She panics, trying to hide the evidence and keep her dad out of her lock-less room. She barely makes it there with some makeup still on her face. Elrich grows suspicious.

The meeting opens Julie up to a world of confidential information. Central Park isn’t safe at all. The rats are on the verge of an uprising, and last night was the closest they’ve come to accessing the weapons depot. Julie is being used as a scapegoat to justify a possible offensive strike against the rats - because she was “kidnapped” during her patrol. Julie can’t tell them the truth because they’ll never believe her and… rats are the ENEMY! They put her on the spot, and she lets something off-color slip out when describing the night: “He was hairy– I mean, it was scary!” During the meeting, Julie also catches a glimpse of the heavily guarded vault, where Squirrel secrets are kept, including their most prized possession - an old, vintage BOX. After the meeting, Elrich gets a talking-to from the council. They expect him to turn Julie into a proper squirrel. “Don’t let your past cloud your judgment, Elrich.”

Julie manages to dress up like a rat again and sneak out, walking right down the main road, oblivious to how many people are running away from her, now that she’s dressed like a rat. She reaches Huddlestone Arch - the rat quarters - and goes undercover into their world, looking for Rome.

It’s scary at first, but then she has the time of her life. The rats are very down-to-earth, non-judgmental, fun, and free. She even meets a city squirrel, who is a welcomed guest at Huddlestone. He tells her that this whole social hierarchy is a Central Park thing. It’s not like this everywhere, and most animals want nothing to do with it.

Rome recognizes her and pulls her away, terrified. She CAN’T be here. He tries to get her out, but her tail disguise gets ruined, and he shoves her into a closet, just as Rome’s dad, DON SURCI, the leader of the rat world, arrives. In the squirrel’s eyes, he’s a mafia boss, but down here, he’s so much more.

Rome is the heir to the underworld but despises crime and isn’t being given much of a choice. He’s preparing to run away to avoid being dragged into the impending war with the squirrels that Don Surci wants him to lead. Don Surci threatens him with rats’ most dangerous ally - an OWL named SILENT NIGHT - and then leaves.

Rome is afraid to leave again, but Julie coaxes him out, and they wind up at The Loch, where she gives him a gift - an oreo. They lament that rats and squirrels can’t be together. Rome asks Julie to run away with him, but she refuses, naively believing that things will turn around for everyone.

The next day, Elrich takes Julie to Fry - the local hawk - to check his allegiance before this possible rat war. It’s a terrifying encounter. Julie watches obvious bribery and misuse of important resources unfold before her eyes. She realizes how much of a hold the squirrels have on Central Park. Fry only agrees to help because he has beef with Gule and hasn’t been allowed to settle their rivalry until now because of the rat/squirrel social fabric. Back at Central Tree, a strange new squirrel piques Julie’s interest. It’s Rome in disguise, already making friends with the locals. He’s zealously into the idea of rats and squirrels living together, and pushes Julie to use her position to make it happen. Julie isn’t 100% on board but agrees to go with Rome to consult an old friend of his for advice- a giant tortoise named VICE who lives in the central park zoo and claims to be 140 years old. Julie has always wanted to go to the zoo.

Being a human-sympathizer, she romanticizes the situation of domestic animals and has always wanted to meet them, but was never allowed to. Surprisingly (to her and no one else), the majestic zoo animals are jealous of her freedom.

Vice tells them that rats and squirrels didn’t used to be enemies. Rome and Julie decide that if they can prove that to be true, there might be a way for them to be together and for Rome to stay in Central Park. And if there’s one place to look, it’s the top secret squirrel vault.

There’s no time to get more information, though. Rats close in on Rome and Julie. Rome takes Julie to the best place he knows for an escape - the model sailboat lake, operated by remote controls. After an intense boat chase, Rome and Julie make it back to Central Tree. As soon as Julie closes her window, the wind whistles for a moment, and Gule snatches Rome. Gule delivers Rome to Don Surci, who threatens to kill Julie if Rome doesn’t cough up everything he knows and agree to help the rats take over Central Tree.

Meanwhile, Elrich catches Julie sneaking through her window, and realizes what’s going on. He tells Julie the secret of why the squirrels have to rule the rats. Humans would kill all rodents if they didn’t think some were good and some were bad. The only way for squirrels to be safe is for rats to be turned into the enemy. He shows her pictures and traps from the 1900s, when humans tried to exterminate squirrels.

Julie is totally trapped, as she realizes that this isn’t about whether or not rats can be good. The problem exists in spite of that. Elrich empathizes with her. He knows the pain of this firsthand. He starts to tell her something about his childhood, then holds himself back.

That night, a rock hits Julie’s window, and she finds Rome on the ground. She opens the window, and fails to notice the other rats sneaking in behind him. Rome and Julie go after the vault all too quickly, which obviously doesn’t work. They end up running and hiding from security and wind up in the old school building. Rome is dying to warn her about the break-in, but he’s too afraid.

Julie realizes where they are. She doesn’t need the vault after all… They remove the old tiles in the bathroom, and for a moment, everything stops.

The walls are covered in paintings of old New York, when rats and squirrels lived together in harmony in Central Tree. Through the paintings, they tell the entire story of how the rats immigrated to America on boats and were accepted with open arms by their squirrel cousins until the humans labeled them “diseased” and the squirrels turned their backs on the rats.

Suddenly, alarms blare. The squirrels fight back and get the rats out of the tree before they reach the vault, but Rome can’t escape in time. He and Julie are caught together. The squirrels show Julie how Rome was using her to help the rats break in. Rome tries to deny it, but it’s no use. Julie is thrown in jail, heartbroken, and Rome is thrown back to the rats, to be dealt with however they see fit. If she’s so confident about the rats being equal to the squirrels, then she should have nothing to worry about…

Elrich comes into Julie’s cell and tells her his secret. He was raised in the Found Children’s Orphanage and was best friends with a rat - Don Surci. No one would adopt him because he acted like his rat friend. One day, they both got stuck in rat traps. Elrich was saved by two squirrels, who would end up raising him, but he didn’t go back for Don Surci. He’s always wanted to apologize for abandoning him when he was adopted, but he can’t speak to him ever again because rats and squirrels are forbidden to do so. Julie realizes that she doesn’t want to be the mayor of this broken world the squirrels have built. Maybe she never wanted it. She just wanted to do what was right for everyone.

Meanwhile, Don Surci locks his own son in a cell. The key is jammed into a pipe, with a snail on top of it, suspended over a long drop into deadly water. If Rome steals the key, the snail will drown. He’ll have to become a real rat to get out. Otherwise, he’ll die in there.

Rome watches through the keyhole as the entire rat population embarks on a mission to take back Central Tree by force. They’ve located the vault, and the squirrels know they broke in. The time to fight is now or never. The rats converge on Central Tree. They have the numbers, but the squirrels have the tech.

Rome debates his immoral escape, then refuses, and waits to die in the dark of his cell. Suddenly, a swarm of snails appears to rescue their friend. Turns out, the snails and slugs of Central Park are going through the EXACT same rivalry as the rats and squirrels. Rome watches in shock as the snails forgive their lost comrade in the cutest, squeakiest little snail voices, and free him. In the process, the key falls down the pipe, gone forever. The captive snail’s slug girlfriend forgives him, and both groups hug it out. They’re ready to leave Rome to rot, but the snail he spared returns the favor, and they retrieve the key for him. Rome sprints towards Central Tree.

At the tree, the squirrels are taking a beating. The fish sports announcers comment on the fight, gargling indistinguishably from the water. The rats can’t break into the tree, so they light it on fire. Overhead, Gule and Fry fight it out.

Julie desperately tries to escape, but she can’t. The fire will suffocate her in minutes! A few rats take a wrong turn into the dungeon, so she begs them for help, but they leave her there.

As they climb the stairs, someone knocks them back down. It’s… Elrich! He breaks her out, but she’s stuck at a crossroads. Whichever side she helps will hurt the other.

Suddenly, Julie bolts up the stairs with an idea. She reaches the vault, just in time to see Don Surci stealing the old vintage box from inside it.

The box is open, glowing, and there are tears in his eyes. After all this time, the squirrels were hiding the truth, and now… he’s gonna destroy it forever. Julie lunges to save the box, but the rats hold her back. Don Surci lights a match to the box, just as Rome swoops in and snatches it. “Armed robbery, Dad. You should be proud.” Don Surci is NOT proud. The chase goes up the burning tree - Rome, Don Surci, Julie, and Elrich in the rear.

Rome tries to apologize to Julie, but she won’t hear it. All four of them fight over the box. Rats and squirrels stop fighting and watch the chaos from below. Don Surci gets stuck in a rat trap that was set by the squirrels. Julie slips off a collapsing branch and hangs for her life.

Elrich gets a flashback to Don Surci in the same position in the trap when he was younger. Rome reassures him that he (Rome) can save Julie, and Elrich trusts him. In front of everyone, Rome saves Julie, Julie’s Dad saves Don Surci, and Rome and Julie kiss. Julie opens the box and rains down pictures upon pictures of rats and squirrels living together. The sprinklers come on and douse the flames, and Julie finds the last thing in the box - the deed to Central Tree, co-signed by a rat and a squirrel.

Rome and Julie and their litter of adopted chipmunks get ready for school. Rats and squirrels live together again in Central Tree. The old school building is “renovated,” and the original murals are uncovered. Huddlestone is renovated, under Rome’s supervision, and squirrels move in with the rats. All is well in the world, until a possum shows up. “GET HIM!” the rats and squirrels yell. Julie jumps in between them, and we CUT TO BLACK.