Starting at the southern Queensland border, they set out on an expedition to locate a lost 130-year-old marker along the Northern Territory border. On their way from the Simpson Desert to the Gulf of Carpentaria, they visit the centre of Australia, meet colourful locals, assist in a wild croc relocation, and are taken to rarely-visited sites at Groote Eylandt where stunning Aboriginal artwork sheds new light on the history of the region.