Surly Squirrel (Will Arnett) and the other park animals are living a life of luxury, hiding out in the basement of the nut shop. Food is everywhere and life is good. Andie (Katherine Heigl) is worried about Surly’s laid-back lifestyle. She’s convinced the animals are losing their instincts and becoming, lazy, spoiled and fat. In a freak accident, the nut shop explodes, forcing Surly and the animals to go back to scrounging for food in Liberty Park.
Unfortunately for the animals, the evil Mayor of Oakton (Bobby Moynihan) has other plans for Liberty Park. He’s cooked up a scheme to cash in on the park by bulldozing it and building a loud, dangerous, amusement park in its place. When the bulldozers arrive, Surly and the animals fight back. They terrorize the construction workers and send them fleeing back into the city.
When the Mayor finds out his plans have been thwarted by a bunch of cute fuzzy animals, he vows revenge. He calls in a vigilante animal control squad led by Gunther (Peter Stormare) who promises to take care of the animals once and for all.
Just when it seems like things can’t get any worse, the Mayor’s maniacal daughter Heather (Isabela Moner) dognaps Surly’s best friend Precious (Maya Rudolph). Heather takes Precious home and locks her up with Frankie (Bobby Cannavale), her dim-witted but lovable French Bulldog.
Surly and his rat sidekick Buddy venture off into the city to rescue Precious. The city is a big and scary place. They find themselves in a dark alley, where they come face to face with a ruthless gang of city mice. Surly makes the mistake of antagonizing their adorable leader, and finds out the hard way just how tough a cute little mouse can be. Surly and Buddy barely escape the mouse army with their lives.
After breaking into the Mayor’s house and rescuing Precious, Surly returns home to find the amusement park is open for business. He realizes that it’s now or never. Surly and the animals need to put aside their differences and work together to defeat the Mayor and take back Liberty Park, once and for all.