Four English orphans migrate to Tasmania, to the care of their Aunt Jandie on her farm outside Hobart. Their arrival is greeted with enthusiasm by young farm boy Tas, and weeks of exploration and good times follow before Aunt Jandie goes to hospital, leaving the children in the care of Ma and Pa Pinner, her foreman and housekeeper. A few days of tyrannical treatment by the Pinners forces the children to seek refuge in a secret cave, where they set up home to await the return of Jandie. Despite Pa's repeated efforts to recapture them, the children stay, fending for themselves in the bush, until Nigel's secret trip to town uncovers a plot by the Pinners to abandon the farm and swindle Aunt Jandie.