Plot
At the Australian Wildlife Park in Sydney, zookeeper Chaz Hunt has a show that demonstrates scary and deadly animals. Maddie, an inland taipan, appears regularly at the show but is feared by the public. Maddie is supported by Jackie, a motherly saltwater crocodile, who tells her and her three best friends —Frank, a funnel-web spider, Zoe, a thorny devil, and Nigel, a marbled scorpion— about the Outback, a place recognizable with three mountains where creatures like them belong. One day, Jackie is removed from the zoo after she tries to save Chaz's son, Chazzie, from a moat; the staff and patrons believed she was trying to eat him. Saddened and in despair, Maddie decides to escape to the Outback with her companions to find a place where they can live happily. During their escape, Pretty Boy, a celebrity koala and the group's rival, tries to alert the park's security but is accidentally paralyzed by Nigel when the group try to stop him. The group reluctantly decide to take him with them, but not before he is caught on a security camera exhibiting mouth foam from his paralyzing.
While crossing Sydney Harbour, they run into Jacinta, a great white shark, who is part of a mysterious organization called the Ugly Secret Society (USS) where animals considered "monsters" help each other upon hearing a password("I'm ugly, you're ugly, we should all be this ugly, ugly is the new beautiful"). When they reach Circular Quay, Pretty Boy tries to get the attention of the city for rescue but finds that the world misbelieves he has rabies after seeing the footage and he ends getting chased by an angry mob, which corner him, Maddie, and her friends, but Maddie helps them narrowly escape by saying the USS password, sending the group into the sewers. After getting help from Legs, a Redback Spider and her pack in getting around the sewers, Pretty Boy finds that he is incorrectly reported dead and his popularity has been taken by a quokka named Giggles. Chaz and Chazzie find the group and attempt to tranquilize them, but they escape via an ice cream truck.
At a school in the outer suburbs, after Maddie frees two lovelorn cane toads named Doug and Doreen, the animals get a ride on an excursion bus that takes them to the Blue Mountains. Chaz and Chazzie catch up and the animals get in the bus to hide, but inadvertently cause the bus to be pulled over, allowing Chaz to enter to search the vehicle for them but an Aboriginal girl named Norine allows them to escape. However, Chaz throws Pretty Boy out a window and Frank accidentally sends himself, Maddie, Zoe, and Nigel falling off a cliff, landing on a unconscious Pretty Boy in the process.
Maddie argues with Pretty Boy, who berates her for ruining his popularity and breaks down, but when Maddie tries to comfort him, he bursts into a fit of laughter. At that moment however, Chaz falls off the same cliff as the group did and lands on Maddie, Frank, Zoe, and Nigel, who end up getting all over his face, causing Chaz to panic and he throws them off his face but, in doing so, unknowingly pins Maddie to the ground with a stick. Horrified, Frank, Zoe, and Nigel try to save her, but they fall into a pit that Chaz seals off. Having assumed that Chaz had been trying to rescue him, Pretty Boy gleefully approaches Chaz for him to take him home, but he kicks him away and prepares to sedate Maddie. Feeling betrayed, Pretty Boy says the USS password, which alerts some Tasmanian devils, Dave, Lucifer, and Beelzebub, to their presence. After the animals escape, Chaz reveals to Chazzie that his adventurous and Aussie wildlife expert history was all a lie and he only moved from Florida to Australia after being inspired by television shows featuring Australian zookeepers. He decides to make it up to Chazzie by really going after the animals and bringing them back to the park, though Chazzie is no longer sure about the mission.
Over the next few days, the animals are helped by many creatures of the USS (which include Clive, a dung beetle, Vlad, a bat, Susan and Deirdre, two Razorbacks, and Phil, a platypus) on their way to the Outback, while Pretty Boy bonds more with the creatures. One night, Maddie sings a lullaby that she had sung at the park ago & was her only memory of her mother: she was washed out of the nest as an egg by a flood and after a perilous journey, was found on the road by Chaz. Pretty Boy reveals that he was also orphaned, with his mother being killed by a moving car. The next day, Pretty Boy finds a tree of koalas, led by a female koala named Skylar, and foolishly leaves the other creatures, to their dismay and Maddie's relief.
Maddie and the others reach the three mountains. Not long after they arrive, Chaz, with the help of a biker gang from a pub, rounds up and captures Frank, Zoe, and Nigel. Chazzie runs into Maddie and is initially scared of her, but warms up to her upon seeing that she is just as scared as he is of her. Chaz, having misinterpreted Chazzie's encounter with Maddie as catching her, captures Maddie as well and places the creatures in boxes in the back of his jeep, but Chazzie sets Maddie free without his father looking but makes no effort in freeing her friends.
Maddie, who broke down crying over losing her friends, tries to get the animals of the land to help her rescue them, but they initially refuse due to the fact none of them had ever left before. However, Pretty Boy, having found life with the other koalas not as great as he thought due to Skylar being overly chatty and shallow, returns. He cheers her up and asks her to go to the rescue. Using a fire truck, they catch up to the truck and try to break them out. The rescue becomes a disaster when Pretty unmounts the truck to help Maddie, causing the ladder to spin uncontrollably just as Maddie accepts her friends as her adopted siblings, resulting in Zoe taking advantage of Nigel's fear of the color beige to make him emit a high pitch screech to break the glass, which even Zoe believed was unbreakable due a sticker meant to discourage humans from breaking it.
Using one of bikers bikes, Maddie and Pretty reunite with their friends and are chased into a canyon, where the Outback inhabitants, having changed their minds about not helping Maddie, and even the other koalas arrive to help, but everyone is caught in a trap sprung by Clive as a way to get revenge on Chaz for the loss of his brother Duncan, who, prior to the events of the film, tried to escape but ended up getting eaten by a seagull. As a result, they reach a cliff where Chazzie is left dangling over the edge on the ladder. While trying to save Chazzie, Maddie finally stands up to Chaz and tells him that, despite being the dangerous snake on the planet, she is not the monster he says she is and bites his wrist band to help Pretty Boy pull Chazzie to safety. As Maddie is revealed to have molted afterwards, Chaz fully sees these creatures as heroes and decides to let them return to the wild.
As the Outback inhabitants celebrate the group's heroism, they reunite with Doug and Doreen, who now have numerous children which swarm Pretty Boy, and Jackie, who is revealed to be the head of the USS and had escaped by knowing a few tricks to do so & then ordered the USS that she had founded during her lifetime to help the group on their journey, and they all join their new life in the Outback.
