"It's got the children, it's got the locations that are kind of dank and sinister but beautiful. It's sort of like a Grimm fairytale," says Jones.

"It's a dark story, and it's got a lot of human frailty: how do people get involved in a cult, what draws them in, how do they do things that they would normally find morally reprehensible. It opens up a lot of questions that are universal rather than relevant only to this particular group."

Founded in Ferny Creek in the mid-1960s by Hamilton-Byrne and the physicist Raynor Johnson, The Family flew largely under the radar until a former member went to the police with her tale of emotional and physical abuse in 1987.

The cult's property on Lake Eildon was raided and six children taken into protective custody. Like others in the sect, they'd been dressed identically when they were young, many with their hair dyed blonde and cut in the same bob style.

Hamilton-Byrne claimed the children were all her biological offspring, though many had in fact been spirited away from their birth mothers by a network of cult members working in the health system.

Several of these now-adult children are interviewed in The Family, and they speak of being beaten, of being starved as punishment, of being forced to take LSD and other drugs. "There were occasional mentions of sexual abuse," Jones says, but the film doesn't really go there "because it wasn't the predominant experience and it wasn't what everyone talked about".

Still, it lurks there just out of reach, as does the suspicion that the networks that allowed the cult to flourish extended far, wide and rather high into Melbourne society.

"Raynor Johnson had connections to all sorts of people," Jones says. "He and Anne recruited doctors, lawyers, architects. They only recruited really wealthy people, in fact, or people with status and skills they needed."

All told, there were 28 children in the sect, 14 of them living permanently on the Eildon property. "But there were also the children of members of The Family who were affected in some way," Jones says. "There are circles, ripples, different levels of damage in those kids."

Though Hamilton-Byrne, now in her 80s and living with dementia in a nursing home, no longer actively leads The Family, it is still active. Jones estimates it has between 20 and 30 members "with varying degrees of loyalty" in Melbourne. There are branches in the US and UK too.

"It's extraordinary how many people you talk to who were part of it," she says. "It's much bigger than you think it is."

Rosie Jones has also collaborated on a book about the cult with Age journalist Chris Johnston. It will be published in Australia when the film gets general release early next year.

The Age is a media partner of the Melbourne International Film Festival, which runs July 28 to August 14. Screening details at miff.com.au

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