The walls are built of local Finlayson granite, laid in rough courses and cemented with a mortar of burnt coral and beach sand. They belong to the trade in beche-de-mer, the sea cucumber prized as a delicacy in China. Harvesting it along this coast went back centuries, carried out by fishermen from Sulawesi who boiled and smoked their catch in shoreline camps. Europeans took up the trade in the early 1800s. A short-lived venture settled this bay in 1860 and likely raised the first stone building before it was abandoned in 1861, after several of the party died. In 1879 Captain Robert Watson and his partner established a processing station here, with a dwelling, a smokehouse, and a small garden of fruit and vegetables tended above the beach.

In May 1880, Robert Watson married Mary Oxnam, twenty years old, who had emigrated from England with her parents in 1877 and worked briefly as a teacher. She moved with him to the island. Two Chinese men, Ah Sam and Ah Leong, were employed to help in the house and garden. Mary returned to Cooktown in March 1881 to await the birth of her first child, a son named Ferrier born early that June, and was back on the island by July. It was an isolated, precarious life: a young mother, a newborn, and two workers on a remote granite island, with the nearest help days away across the reef. What none of them seems to have understood was that the station stood on ground sacred to the Dingaal, near a place used for the initiation of their young men.

On 1 September, Robert Watson and his partner sailed two hundred miles north to find new fishing grounds, expecting to be gone six weeks. Mary was left with her baby and the two Chinese workers. Late in the month, Dingaal men came to the island, to country that was theirs and a site that was holy. Around 29 September they speared and killed Ah Leong as he worked in the garden, a quarter-mile from the house. They gathered on the beach below the dwelling the next day and scattered when Mary fired a rifle and revolver; on 1 October they returned and speared Ah Sam, wounding him badly. This was not a tale of marauders and a defenceless innocent, as the colony would later cast it. It was a collision between people defending a sacred place and a family who had, unknowingly, built their home upon it.

Cut off and afraid, Mary made a desperate choice. She packed food, water, a few belongings, and two paddles into a cut-down iron ship's tank, one of the very vessels used to boil the sea slugs, and on 2 October set out into the open sea with the baby and the wounded Ah Sam. They drifted for days and reached a small island in the Howick group that, cruelly, had no fresh water. There they waited for a passing steamer that never stopped, and there they died of thirst. Mary kept a brief diary throughout; her steadiness and her care for her child fill its final pages. The last entry is dated 11 October 1881. A passing crew found their remains on 19 January 1882, and Cooktown gave Mary, Ah Sam, and baby Ferrier a vast public funeral.

The aftermath was its own tragedy. A punitive raid went out, and many Aboriginal people were killed, among them people at Cape Flattery who had nothing to do with the events on the island. The Dingaal traditional owners regard this ruin as a symbol of the end of their traditional ways, their displacement, and the violation of their sacred sites. Whether Mary ever truly lived in these particular walls is, oddly, uncertain, but it scarcely changes their meaning. Lizard Island became a national park in 1939, and a luxury resort now stands to the west. The stone tank that carried Mary to her death spent years on display in the Queensland Museum. The ruin endures above its perfect beach, asking visitors to hold two kinds of grief at once, and to grant dignity to everyone the story claimed.