Mr. Thornhill's Villa provides a brief summary of the events that occur after the bloody dispersal of the Aborigines. The original settlers have been replaced by new ones, except Mrs. Herring, who retreats into semi-isolation after the massacre. With the 'native problem' solved, the settlers flourish along the river. The farms and township grow ever bigger and richer. William repays Mr. King the original loan of £115 and borrows £300 more to build a new boat called the Sarah. The two boats continually ply their trade on the river. Thornhill's Point becomes a by-word for success, and William is now a respected member of the new gentry.
William builds a large stone house and names it, as is the custom of landed gentry. Sal decides to call the house Cobham Hall, after the grand house where her mother worked in service before she married Mr. Middleton. The house is on the rise, directly over the rock with the drawing of the fish and the Hope. William orders a pair of stone lions for the gate posts, in imitation of the lions at the entrance to Christ Church in London. He is disappointed when they arrive. Instead of raring up with teeth bared, the lions rest on their haunches, as if in front of a fire. William places them at the top of the gateposts, announcing to the world that he is king of Thornhill's Point.
Over the years, Sal settles in to life at Thornhill's Point. She stops marking the days on the tree, and the idea of returning home drifts further and further away. She still speaks nostalgically of London and the world she left behind. New South Wales is home for her children, and Sal would never leave them to return. Sal turns her attention to recreating her sense of 'home' at Cobham Hall. Just as she made a yard around the little hut to separate nature from civilization, Sal has a large stone wall built around the entire garden. She wants 'real' trees and has an alley of poplars planted from the river all the way up to the house. However, both her traditional English garden and the alley of poplars wither in the hot climate. Sal bears William one more child, a girl called Dolly. Freed from all the household chores by a legion of servants, Sal grows stout and satisfied.
William adopts a new past to better fit his new life. Instead of his poverty-stricken life in the filthy streets of London, William spreads the story that he was born in the clean air of Kent and got caught smuggling French brandy on his own boat into England. He was spared the noose because he often worked for the Crown, smuggling English spies into France. William turns Sal into the daughter of a wealthy ship owner and spins a tale of a romantic elopement. William and Sal never discuss what happened up at Blackwood's place. She never asks, and he never tells. Deep down, Sal knows what it took to ensure their success and security.
Thomas Blackwood lives defeated and miserable in his hut up the river. The lash of Smasher's whip left him practically blind. William plays the noble gentleman and brings Blackwood goods from time to time. Blackwood does not speak to William and ignores William's nervous chatter. William feels the emptiness once filled by the woman and the child. Dick now lives with Blackwood, running the still and delivering rum up and down the river. Shortly after the massacre, Dick left home and came to stay with Blackwood. Although still only a boy, he refused to come home when William found him with Blackwood. Many of the new settlers along the Hawkesbury do not know that Dick is William's son and refer to him as Dick Blackwood.
The battle at Blackwood's forced the Aborigines out of the area. Many of them retreated to a reserve set up by the Governor of New South Wales and became dependent on the government. The considered opinion was that they were a weak race and would soon die out. Long Jack occasionally returns to Thornhilll's Point. The shot to the head from Smasher's gun did not kill him, but it left him physically disabled. His body is crooked, and one leg drags behind when he walks. Emotionally, the battle broke something inside him. Long Jack sits by a fire at the point, just feeling the land beneath him. He refuses the clothes Sal gives him and does not cultivate the little garden she sets up for him. William feels guilty about Long Jack and tries to give him a blanket to keep warm in the winter and tells him to get some food up at the house. Long Jack ignores him. When William touches him, Long Jack says no. He has learned some English. Long Jack slaps the ground and says, "This me. My place." Annoyed by Long Jack’s continuing claim to the land, William storms off and does return.
William ends each day on the veranda with a drink and cigar, watching the sun set over his land. He watches the light change over the cliffs. He often thinks he sees a human being standing on the edge of the cliff. He peers at the shape through a telescope, trying to see if it really is a man. Although he knows that the Aborigines have left the area, still he looks, hoping to see the tall figure of a man looking back at him.
In the final chapter of the novel, Grenville clearly conveys the triumph and loss of that crucial period in Australian history. William's life is filled with the trappings that define him as a member of the gentry. He assiduously acquires material possessions to prove that he is no longer a poor waterman: a fine house, 300 acres of land, a stable full of horses, boots for his children, servants, a stout wife, the finest tea and liquor, even a full-length portrait hanging in the drawing room. However, the episode with the lions symbolizes the inherent superficiality of these trappings. The lions at Christ Church scared William as a child. They symbolized the power of the ruling classes, the power that a young boy born in Southwark could never hope to achieve. When William does attain a place of standing, he wants the lions to announce his power to the world, just as they did at Christ Church. However, their calm mien does not inspire the same fear. While the power of the Church and the ruling class in England is embedded in history, William's power is new, an almost transparent film over the disenfranchisement and poverty of his youth.
William's decision to build the house directly on top of the rock with the drawing of the fish symbolizes his ultimate claim to the land. He literally covers up the proof of the Aborigines’ centuries-long existence on the land, hiding it from future generations of Australians. William reflects that while his children may remember the drawing, their children's children would never know what lay beneath their feet. Grenville is referring to the lost culture of the Aborigines and the ignorance many Australians have about the people who first lived on the land. After William's time, white Australia will develop from a dependence on English culture into a vibrant new society. However, they will forget about the people whose drawings burn brightly under the solid floorboards of their houses.
Sal's tall wall around the garden symbolizes the triumph of the settlers' desire to conquer the new continent. Sal carves a piece of England out of the wilds of New South Wales. She plants a traditional English garden with daffodils and roses and an alley of poplars, 'real' trees. There is only one entrance to the garden, symbolizing the tenacious hold that the early settlers kept on their memories of their former life. Wild Australia remains outside, while they build a recreation of a lost world inside the high walls. However, Grenville points out that this division cannot last - the real Australia will creep its way back in and become an inseparable part of the lives of future generations. The flowers wilt, and the poplar trees die. The only plant that flourishes in the garden is bush of geraniums given to Sal as a cutting by Mrs. Herring, one of the few settlers who learned how to live in harmony with her environment.
Thomas Blackwood is left almost totally blind from the lash of Smasher Sullivan's whip, symbolizing the death of Blackwood's vision of a peaceful co-existence with the Aborigines. Dick represents the Australian youth that could have been if the path of co-existence had been allow to develop. Dick retreats from the world that choose violence over compromise, a world driven by the need to conquer and claim possession. While Willie follows his father's example and settles his own track of land, doing his bit to claim the land for the British Empire, Dick disowns his father and chooses Blackwood's doomed but humane path.
While William has everything that he has ever desired, he is haunted by the ghostly presence of the people who never relinquished their spiritual ownership of the land. Although Long Jack has learned a few words of English, he refuses to conform to the desires and expectations of the white settlers. He does not wear their clothes or become the dependent inferior they want him to be. Long Jack's intransigence and simple insistence that he is a part of the land exposes the shallowness of William's trappings of possession. Long Jack's presence reminds William that Thornhill's Point is not really his and that deep down he is still the waterman who stood knee-deep in cold water bowing and scraping to the gentry.
Grenville ends the novel with the image of William sitting on his veranda, scanning the horizon for the shape of a man. While William has carved out his kingdom, he is aware that there is another Australia beyond the tilled fields and fenced lands. The invisible presence of the Aborigines high on the cliff hangs over not just William but all of Australia, for generations to come.