Thrown from her horse deep in the bush of Waratah National Park, Clancy is hopelessly lost and her mother is due at Ranger Headquarters to see how Head Ranger Matt Hammond has been looking after the teenaged house-guest. A band of aboriginal nomads find Clancy and bring her back to headquarters, just in time.
Sonny has been placed in charge of an automatic recording unit deep in the bush of Waratah National Park, supervised by his father, Chief Ranger Matt Hammond. While servicing the box, Sonny finds an Air Force pilot who has ejected from his airplane. In trying to rescue him, Sonny slips and becomes trapped on a cliff face. Skippy goes for help and returns with Matt who rescues Sonny and, with help from Mark and Jerry in the helicopter, the pilot as well.
Alone at Ranger Headquarters, Jerry is overpowered by burglars who take everything movable. Later, Sonny and Skippy come across a group wearing Ned Kelly armour entering a cave. Sonny suspects they are the burglars, but they turn out to be a pop group, 'The Bushrangers', who have set up their instruments in the Park after being driven from their town by neighbours complaining about the noise. The group eventually help catch the burglars after a sloppy mud fight.
Sonny and Skippy discover the hidden entrance to a remote valley, thought to be inaccessible and uninhabited. There Sonny makes friends with an old Aboriginal living alone, whose tribe has long since migrated to other parts of the country. One day Sonny finds Tara weak and in a semi-coma — he believes he has been visited by a 'death spirit' and is going to die.
Dr Stark sends an operative into the park to collect a rare ant-eater specimen using a special gas-emitting camera. Clancy stumbles across the collector and is temporarily paralysed by the device. Skippy returns an incriminating audio recording of the encounter back to the ranger HQ leading to the thief's capture and Clancy's safe return.
Matt Hammond's boss and a government Senator decide to sack him after it appears that Matt has run their car off the road and threatened them. It transpires that Dr. Stark has hired an actor to impersonate Matt Hammond in order to discredit him, but the whole scheme backfires and Dr. Stark has to honour the promise of a $10,000 donation to Waratah National Park.
Sonny, helped by Skippy, takes a job with a team of sheep shearers, not knowing they are rustlers, to earn money to buy a birthday present for his father. His absence from home puts Matt Hammond on the track of the three strange characters who have developed a variation of sheep rustling — they only take the wool!
Ranger Headquarters is cut off by a violent storm as Matt Hammond lies poisoned by a snakebite. The phone line is down, the radio is not working, the serum is lost in the creek, the helicopter is out of fuel, the bridge is out and the ford is flooded. Skippy crosses an impassable gorge to fetch help, and the life-saving serum is parachuted to Ranger Headquarters just in time.
A diamond thief loses a valuable necklace while on the run from the police in the park. The thief sees Skippy find it and places it in her pouch and follows her back to the ranger station where the Hammonds are busy building a parade float. The thief stows away on the float and a dramatic fight breaks out when he tries to recover the necklace as the float makes its way through the streets of Sydney.
Sonny paints a picture of Skippy for his art class but before he mails it in, Mark replaces it with a 'better' one he made to help Sonny get a better grade. Sharing Mark's good intentions, Clancy unknowingly swaps Mark's painting for her 'better' version but when the painting is entered in a prestigious art competition and talk of an art scholarship begins, Clancy and Mark must come clean.
Sonny's birthday wish comes true — a ride in the helicopter, but not the way he expects. While flying over Sydney, Flight Ranger Jerry King collapses, leaving Sonny alone with the controls. To save their lives, Matt tries to use a tranquilizer gun to deliver the medicine to Jerry while flying alongside. When that fails, Sonny must be talked through landing the helicopter on his own.
An old tramp, Trundle, looking for odd jobs, fascinates Sonny with tales of adventure. However, Matt Hammond believes the stories are figments of Trundle's imagination and considers it a bad association for Sonny. Trouble begins when the old swagman gives Sonny an expensive antique watch as a parting gift. Matt discovers the gift, asks the police to trace the owner… and discovers the Swagman's secret. Trundle turns out to be Miles Vincent Archer, the wealthy chairman of a vast corporation.
Matt Hammond is faced with a human problem when one of his rangers moves to a new nature reserve up north, taking his wife and sons but leaving his daughter Clancy, who has exams pending, to board with the Hammonds. Clancy is in trouble from the moment she comes to stay, and she gets the idea she is not wanted and runs away.
Mark is unhappy when his father, Matt Hammond, tells him to accompany a marine biologist who wants to collect underwater specimens. But his misery turns to delight when he discovers that the marine biologist is a spunky young woman. The two of them quickly find themselves having to rescue Skippy and an unconscious Sonny from an out-of-control speedboat.
A mysterious disease threatens to wipe out all animals in Waratah National Park, and evidence points to Skippy as the carrier. Sonny is heartbroken at the possibility of losing Skippy, and disappears into the bush with the kangaroo. There he comes across a poacher, and Dr. Steiner discovers that the poacher's dogs are the actual carriers of the disease.
Sonny, Mark and Jerry investigate an expensive game fishing cruiser with three men aboard after Skippy and Sonny came across men trapping animals in the bush at night. Swimming out to the cruiser, Jerry overhears a conversation which indicates the men are stealing koalas for Dr. Stark's private zoo.