Two Cowichan tribes lived on Thetis before European contact - the Yekolaos and the Lilmalche - and their presence here long predates any of the names now printed on the chart. What happened on the island next door is inseparable from that history. The Kuper Island Indian Residential School operated on Penelakut from 1889 until 1975, taking in Indigenous children from across this coast for most of a century. On 12 July 2021 the Penelakut First Nation announced that more than 160 unmarked graves had been located on the grounds and foreshore of the former school. Those were children, brought here from their families, who never went home. The two islands sit a few dozen metres apart. Visitors to Thetis are looking directly at Penelakut from most of its southern shoreline, and it is worth knowing what they are looking at.

Thetis and Penelakut were once a single landmass, joined by a low neck that boats had to go around. In 1905 a canal was dredged through it - Canoe Pass - turning one island into two and saving small craft a considerable detour. It is a modest piece of engineering with an outsized effect on how the place is understood. On the chart they are now separate islands with separate names, separate jurisdictions, and separate histories, when the geology says otherwise. A hundred and twenty years on, the ditch is still doing the work of a border.

Thetis runs roughly three miles north to south and two miles across, its shape defined by two parallel ridges. Burchell Hill tops the western ridge at 503 feet; Moore Hill crests the eastern one at 511. Between and around them, the forest is classic dry-side Gulf Islands - Douglas fir, western red cedar, and arbutus, the copper-barked broadleaf evergreen that only grows where the summers are dry enough. That dryness is the island's defining climatic fact. Sitting in the rain shadow of Vancouver Island's mountains, Thetis gets substantially less rain than the west coast a short distance away, which is why the vegetation looks Mediterranean rather than sodden. Pilkey Point on the northern shore is where islanders go for the view out across the water.

European settlement started in 1874 but did not really hold until the 1890s and 1900s, arriving in the piecemeal way that Gulf Islands settlement usually did: one surveyed lot at a time, changing hands between neighbours. In 1891 Peter and Joseph Hunter bought lot 27 from a Mr. Walls, and a couple of years later added lot 18, purchased from Olaf Gustafson. Descendants of Peter Hunter still live on the island's northern coast - a continuity of more than 130 years on the same shoreline, which on an island of a few hundred people means the Hunter name is simply part of the local geography.

For its size, Thetis maintains a surprising amount of institutional life. Capernwray Harbour Bible School and Pioneer Pacific Camp both operate here, bringing seasonal populations of students and campers. The Thetis Island Nature Conservancy runs art- and science-based education through its Nature House program at The Portal, a 70-acre waterfront property given over to conservation, stewardship, and local food production. Two marinas anchor the social geography - Telegraph Harbour with a bistro, Thetis Island Marina with a pub - alongside a small convenience store that houses the post office and several bed and breakfasts. And the schoolhouse still runs, all grades in one room, one of the very few left in the country. It works for the same reason everything else on the island works: there are 379 people, and everyone has to do more than one job.