A schoolmaster finds an unconscious young man on his doorstep, takes him in and looks after him. A firm friendship develops between the stranger and the headmaster's children, Bernard and Jean and their friend Peter, and this leads to them discovering the stranger's secret –- that he is from another planet and has been sent to find a new home on Earth for his people. The stranger, Adam, is joined by fellow alien, Varossa. They live in a society without books where they memorise everything. In the second series the children have to enlist the help of the Australian Prime Minister when Peter is kidnapped by the alien, and a procession of intrigues eventually leads them to the aliens' home planet of Soshuniss.