A bridge across the Torrens River, near the University of Adelaide, was an established homosexual beat in the 1970s and before. That was where men went to hook up for sex, in an era when homosexuality was still illegal in Australia.

On 11 May, 1972, Dr. George Duncan, a visiting Englishman and professor of law at the University, was thrown into the fast-flowing river from this bridge by three unknown men. He subsequently drowned.

He was not the first nor the last to suffer this fate, but his case raised questions in Parliament. Rumour had it that members of the SA Police’s Vice Squad were responsible, and that they frequently amused themselves by chucking poofters into the river.

Duncan’s death was indeed a watershed, because it led to a change of law: homosexual acts (with various provisos) were subsequently decriminalised in South Australia prior to anywhere else in the country.

Macon Escobal Riley and Tomáš Kantor in Watershed. Photo © Keith Saunders.

That is the basic story of this remarkable piece by playwright Alana Valentine, novelist Christos Tsolkas, and composer Joseph Twist. The work received its premiere in Adelaide (where it got...