In a 1950s era Australia, Sydney is under siege by giant carnivorous animals from the outback. A new expedition is planned to uncover the secret of the powerful Ayerstone which caused vast magical changes in the wildlife, along with attempting to find a fortune in valuable opals. A meeting is organised and in attendance are the allied leaders of the city: the boxing champion of the kangaroos, the Lord Mayor of the wombats, King Larrikin of the kookaburras, and Prime Minister Koullas of the humans and koalas.
The proposed route of the expedition is explained by a soldier during the briefing: "the consensus is that our best bet's to head through the Blue Mountains to start with, bypassing the thickest concentration of spiders that infest destroyed towns along the main highway. We can also try and make contact with the flying foxes at Jenolan Caves. Afterwards we make our way back through old sheep farms towards Lake George, and pass by the ruins of the former capital. Beyond that's the high country and we'll make for the Snowy River, cross the Murray near its source, then travel through bushland to Wangaratta. We look for the opal collection believed to be in the bank's vault, and whether or not we find them, we'll head back through the bush towards the Dandenong Ranges, on the edge of Melbourne. We skirt around that ruined city southwards, along the coast towards Wilsons Prom. There we'll try and find this stone from Ayers Rock which Bruce's uncle may have hidden. If it's there or not, we'll return by the same route. That's the rough plan, but of course, as we don't know much about what the area is like now, we may need to change it based on what we see out there."
The ten expedition members are comprised of a mixed assortment of humans and animals. 'Wallaby Bruce' Buckley, a 14 year old from the Sutherland Shire, whose uncle removed the Ayerstone thirty years ago. 'Outback Jack' Macdonnell, an adventurer, obsessed with finding the lost opals from Wangaratta. Darren Eagle, an Aboriginal soldier and bush tucker expert. Myles Mulligan, an Army captain and rifleman. Rachel Shearer, a wildlife expert from Taronga. Walter Diggins, a wombat, warrior and wombattalion leader. Larry Larrikin, a kookaburra and guard of King Larrikin. Carlo Koullas, the koala, medic and cousin of the prime minister. Preston Pierce, the platypus, commando with the SAS. Maru Hopper, the grey kangaroo, Bruce's mate from way back.
Together the expedition marches into the dangerous lands outside of Sydney, going through a variety of environments; deep canyons, underground caves, grassy plains, tall forests, snowy mountains and fast moving rivers. The group have adventures dealing with bushfires, floods, storms, bad weather and other forces of nature. They soon find the bushland has many threats, while towns have been destroyed and are now overrun with giant spiders and insects. It seems these changes in the landscape were caused by the piece of Ayers Rock which was removed, which increases their desire to find it. They encounter many animals, both helpful or a hindrance: flying foxes, bats, birds, snakes, lizards and marsupials.
