Ellie goes out camping in the bush for a week with her friends Homer, Lee, Kevin, Corrie, Robyn, and Fiona. Later on, they find Chris, one of their school friends. They find a way into a large, vegetated sinkhole in a remote area of bush the locals have dubbed “Hell”, and camp there for the week. During this time they see large numbers of planes flying through the night without lights, and though it is mentioned in conversation the following morning, they think little of it.
When they return home they find that all the people are missing and their pets and livestock are dead or dying. They come to realize that Australia has been invaded and their family and friends have been taken prisoner.
Avoiding capture by enemy soldiers, the group returns to Hell and after short period of recovery start making plans to fight back. Over the course of the first three books in the series, the group succeeds in destroying a bridge that leads into Wirrawee, an enemy convoy; several houses that are being used by the enemy as a center of operations and a nearby strategic harbor.
The surviving members of the group are eventually captured and placed in a maximum security prison. During an air-raid by the Royal New Zealand Air Force the group escapes, but loses yet another member while doing so. They encounter a downed RNZAF pilot and arrange to be evacuated to New Zealand.
Book four, Darkness, Be My Friend, takes place several months later. The group is trying to live a normal life in New Zealand with other refugees, but are haunted by their memories of the war (which is still ongoing). They are approached by the New Zealand Defense Force, who is seeking Australian guerrillas to act as guides for saboteur units that are being dropped into occupied Australian territory. The group returns to Wirrawee, their hometown, accompanied by a platoon of New Zealand troops.
The New Zealanders go missing while on a mission to destroy Wirrawee Airfield (which is being used as a major military airbase). Alone behind enemy lines once more the group decided to attack the Airfield themselves. They fail and return, depressed, to Hell. Soon after, through sheer luck, the group find themselves perfectly positioned to attempt another attack on the Airfield. This time they succeed, and manage to destroy a majority of planes on the airfield. After the attack, the group finds their way to the nearby city of Stratton. In Stratton they discover a tribe of feral (and hostile) children, who have been living on the streets and hiding from enemy troops since the war began