There were other murders, at Boney Point, Butchers Creek, Slaughterhouse Gully – the names are grotesquely eloquent. When the first European settlers arrived in Gippsland, 1,800 Aborigines lived in the area that had been their ancestral home for some 20,000 years; by 1854, only 126 remained, mirroring a nationwide pattern that led later historians to conclude that Aborigines had, in the words of John La Nauze, been little more than a “melancholy anthropological footnote” to the continent’s history.

The leader of the Highland Brigade and the first European to open up the region, Angus McMillan , was himself the survivor of a ruthless campaign of dispossession. He had left for the colony of New South Wales in 1837 to escape the terror of the Highland Clearances, in which thousands of his fellow Scots were evicted from their tenancies during Scotland’s agricultural revolution. McMillan is still celebrated in his native Skye and in Australia – where he is honoured with cairns and plaques – as a pioneer, a man of great personal integrity and a pillar of settler society. The diary he kept during his passage, in which he records his resolution to be “humble, meek, diligent and industrious, charitable even of aliens”, makes for pathetic reading. For as Cal Flyn – who is a collateral descendant of McMillan’s – reveals, he is equally deserving of the alternative title given to him by the aboriginal community: “the Butcher of Gippsland”.

Vexed by the puzzle of her relative’s transformation, within five years of arriving on those shores, “from virtuous Presbyterian lad to cold-blooded killer”, and with a dim idea of making reparations to the descendants of his victims, Flyn – who grew up in the Highlands – sets out for Australia. Once there, she realises that she has stumbled into an ethical morass far murkier than she ever bargained for. In this country where “nothing looks or works quite the way you expect”, Flyn deftly captures the looking-glass world of the antipodean landscape, so alien to European eyes – where, as one early settler wrote, the “swans are black, the eagles white, the cod fish is found in rivers and perch in the sea, the valleys are cold and the mountain tops warm”. Her account is vivid with a sense of its strangeness; lyrically responsive to the odd local fauna and flora, the wombats with their humanoid waddle, the layered rocks, “red-raw but delicate as millefeuille”, the “hazy antiseptic perfume of the eucalypt”.

The settler response to this otherness was to make it familiar. On gazing at the Gippsland plain with its kangaroos and wild swans, encircled by sheer mountains, plunging gorges, a forest of thorns and a roiling sea, McMillan saw in it “a country capable of supporting all my starving countrymen” and promptly christened it “Caledonia Australis” (it was later renamed after the governor of New South Wales, George Gipps). When choosing names, unoriginality was key: Lake Victoria, Port Albert; even an Avon river with a town on it called Stratford. Having made the leap from crofter to laird, McMillan presided over his own property, a 60,000-hectare estate named Bushy Park, in a tweed three-piece suit and a tartan bonnet.

Of course, the land was not unoccupied. The Gippsland plain was the base of the Gunai , one of several hundred Aboriginal nations on the Australian continent with an unbroken presence there since the Stone Age. As Flyn points out, the first European arrivals were “baffled by these eccentric natives”, who lived a purely nomadic existence, did not farm or graze livestock, and lacked a recognisable hierarchy or concept of land ownership. Unable to identify “any Aboriginal leaders with authority to negotiate”, they did not negotiate at all, declaring Australia terra nullius, no-man’s land (a formulation that was not definitively overturned until 1993 with the passing of the Native Title Act, which acknowledged original Aborigines rights to crown land).

The resulting territorial wars were bloody in the extreme. Although the government never adopted a policy of extirpation, the settlers’ agenda was implicitly genocidal, spawning the sort of doublespeak typical of such systems: the Gunai were not “murdered”, they were “dispersed” or “chastised”. The killing of Aborigines was steeped in secrecy. Officially it was punishable by hanging, but as one squatter lamented, it was utterly impossible to bring forward “valid evidence to convict in a court of law”. Hunting aborigines became an acceptable sport; even the crown commissioner took part.

The Gunai, meanwhile – resistant to being relegated to an anthropological footnote – were not passive victims, waging a gruesome form of guerrilla war that terrified the whites. The massacre at Warrigal Creek was, predictably, a reprisal for the murder and mutilation of the nephew of a local landowner. If the clue to McMillan’s brutalisation can be found anywhere, it’s here, in the psychological mechanism of warfare, where the enemy stops being a human individual. Occasionally, the Gippslanders’ terror of the “other” took baroque forms. Flyn tells the bizarre story of their hunt for a white woman who was supposedly abducted, raped and disfigured by her aborigine captors. When found, she turned out to be the armless figurehead of a ship that had foundered on the Gippsland coast.

Flyn’s encounters with the Gunai during her trip are sometimes bruising – especially one with a tribal elder who pushes her to agree that her ancestor’s murderous tendencies are “in you, in your blood”. But her anguished narrative suggests otherwise. In the end she steers clear of accepting the notion of inherited guilt, not least because this so often simply leads to token apologies that do little to address persisting inequalities. Thicker Than Water is, to borrow a word Australians use when dealing with anything unsettling, a “confronting” book. The urgent question, “How can things be fixed?” infuses every page. To her credit, Flyn is aware of the ugly likelihood that they can’t.

The Guardian