When Petrie was fourteen, the Turrbal elder Dalaipi took him on a journey that few outsiders ever witnessed. Every third year, when the great bunya pines of the ranges bore a heavy crop of cones, the Aboriginal peoples of southeast Queensland gathered in their hundreds for a feast that was part harvest, part festival, part diplomacy, with messengers sent far across the country to summon distant clans. The boy walked into the Blackall Range and shared in it. It is hard to overstate how rare that was. The bunya gatherings were among the most important events in the region's Aboriginal calendar, soon to be disrupted forever by clearing and settlement, and a settler's son sat among the trees and the fires and remembered it all his life.

In 1859 Petrie married Elizabeth Campbell and went looking for land of his own, and even this he did differently. Rather than simply taking up a run, he asked Dalaipi's advice. The elder's son, Dal-ngang, led him to his people's ancestral country on the North Pine River and offered it, only to learn with indignation that colonial paperwork had already granted it to someone else. Petrie negotiated a purchase and named his station Murrumba, a local word meaning 'good place.' Aboriginal workers helped him clear the land and raise the buildings. The arrangement sat inside a colonial system that was dispossessing the very people guiding him, a contradiction Petrie never fully escaped, but within it he dealt with the Turrbal as neighbours and partners rather than obstacles to be cleared away.

In 1861 Petrie was called before a government committee investigating the Native Police, and his testimony cut against the grain of his time. Where many settlers spoke of Aboriginal people as savages or nuisances, Petrie said plainly that the old Brisbane clans were dying, poisoned by alcohol that whites supplied illegally, and that much of the trouble blamed on Aboriginal people was 'in great measure the fault of the white people themselves, and the way in which they treat them.' He had lived, he noted, where no other settler could remain, with several hundred Aboriginal people around him. His account was not free of the casual language of the era, but it carried something most official voices lacked: first-hand knowledge, and a refusal to repeat the comfortable lies.

Petrie's deepest legacy was written down by someone else. In 1904 his daughter, Constance Campbell Petrie, published Tom Petrie's Reminiscences of Early Queensland, setting down the stories her father had carried since boyhood: Turrbal words and place names, customs, hunting and the bunya feasts, the people he had known by name. The book is still regarded as one of the best authorities on early Brisbane and a precious source on the region's Aboriginal life before colonisation overwhelmed it. Tom Petrie died in 1910, and that year the North Pine district was renamed Petrie in his honour. The name on the map remembers the grazier and the explorer. The book remembers something more important: the world he was let into as a child, and chose not to forget.