Sam and George, 13 and 11, live at Brumby Plains, their parents' sprawling buffalo station in the Northern Territory. They're counting down to the Christmas holidays, and anticipating the fun they'll have exploring the property, horse riding, and spending time with their cousins Tess and Darcy. But weird things are happening at Brumby Plains - who is leaving the gates open, and why did a plane land in darkness in a deserted area? A chance encounter with an Englishman who knows more than he's letting on leaves Sam suspicious, but all their worries are forgotten as the four kids find a spooky cave up in the hills. Vincent, their old Aboriginal friend, says they shouldn't go there - he says it's a dangerous place, full of angry spirits. Surely there's no harm in exploring, though - is there?