The formation of Melbourne-based cult The Family and the behaviour of its charismatic leader – a yoga teacher who claimed, as you do, to be Jesus Christ reincarnated – is a terrific story, full of incredulous events and hair-raising details.

Teaching a hodge-podge of eastern mysticism and Christianity, Anne Hamilton-Byrne was the group’s self-appointed head honcho, who sat on a literal throne and fed her home-schooled young followers LSD.

Throughout the 60s and 70s Hamilton-Byre adopted children she raised (and claimed to be her own), dressing them in identical clothes and cutting their peroxide-dyed hair in the same bob cut. Looking at photographs of them evokes memories of Village of the Damned, or the twins from The Shining (“come play with us forever and ever and ever …”).

Anne Hamilton-Byrne, leader of Melbourne-based cult The Family. Photograph: Melbourne International film festival

A falling out between the leader and one of her “daughters”, Sarah, spelt the beginning of the end: police raided The Family’s property in Eildon in the late 80s and legal proceedings followed. In the field of stranger-than-fiction Australian tales, this one is certainly on the podium.

A terrific story indeed. But sadly, not the one presented in film-maker Rosie Jones’s ambitious attempt to make sense of it; a structurally higgledy-piggledy documentary that is less an expose than a tantalising suggestion of the history lesson that might have been.

The tendency for film-makers to shoot first and “pick it up in the edit” is a particularly tempting one in documentary. Here it seems to have overwhelmed the film-maker; there’s a feeling The Family was ordered retrospectively and the task was monumental.

Jones’s research is commendable (perhaps an upcoming book tie-in will provide a more accommodating format) and the film includes access to several of the now grown-up children.

But the riddle of what compelled Hamilton-Byrne’s followers to behave in ways they would otherwise find morally reprehensible remains largely out of reach. So too for more elementary questions. What did a standard day at the club cult-house look like? What did the adults get up to when they weren’t drugging the kids?

The Family drops most of its information about Hamilton-Byrne towards the end (her life is unquestionably interesting, journeying from an impoverished background to an insanely – in more than a single sense – privileged one) but that content might have worked better front-loaded. The film would have immeasurably benefited from a clearer, more palatable structure, a path to guide audiences through this tangled, creepy, improbable yarn.

At one point a new interview appears, credited as a current member of the sect. The viewer’s response is likely to be What’s that? Say again? This thing still exists?

But the film-maker greets the revelation with no sense of surprise, a frustrating approach, presumably predicated on an assumption audiences more or less know this story. Most of us don’t. A great one remains – evidently, like the cult itself – lurking somewhere, waiting to be told.