The Walsh family welcome a mysterious stranger into their home. Impressed by the man's advanced intelligence and linguistic skills, Mr Walsh offers him a teaching job.
Curious about Adam's weekend bushwalks, Bernie, Jean and Peter follow him to the Blue Mountains where locals have reported strange lights in the sky.
Aboard the spacecraft, Bernie, Jean and Peter learn the truth about Adam and Varossa's people, the Soshunites. Meanwhile back on Earth, the teenagers are reported missing.
On their return to Earth, Adam and Varossa are arrested. Bernie, Jean and Peter have a hard time convincing the authorities that their friends are from another planet and need help.
Professor Mayer meets the peaceful Soshun while authorities on Earth prepare for an invasion.
Professor Mayer takes the plight of the Soshunites to the United Nations.
News that the Earth has been visited by extra-terrestrials sends the world's press into a meltdown. Peter goes on an unexpected journey.
Professor Mayer and his son Edward return to Sydney, pursued by the opportunistic American businessman Rudolph Lindenberger.
Jean, Bernie, Edward and Professor Mayer are spirited out of Sydney to the Parkes radio telescope. Still stranded on Soshuniss, Peter is forced to deliver an ultimatum to the Australian Prime Minister.
Peter's return to Earth sends Parliament House into a panic. Still on the run, Adam attempts to contact Jean and Bernie. Meanwhile, Lindenberger's men close in.
The arrival of Lindenberger's henchmen leads to a dramatic chase across the Parkes radio telescope dish for possession of Adam's radio. With Soshuniss under threat by Earth, Professor Mayer volunteers as a human shield.
Threats of attack by Earth lead the Soshunites to announce they will only negotiate with the children. The Australian Prime Minister outsmarts Lindenberger. (Final)