“You think we’re not at war here? As a Blackfoot woman I can tell you it sure as fuck feels like we are.” So begins Tara Beagan’s one-woman play Deer Woman, about an ex-soldier avenging the murder of her sister – and the 4,000 other Indigenous women and girls who have gone missing or been killed in Canada since the 1970s.

The show, set deep in the woods with nothing but a cooler, holdall and bundled-up tarpaulin as props, is delivered as a mesmerising, shocking, and at times terrifying confession to a smartphone on a tripod. Lila, whose primary goal in life has been to protect her sister Hammy, is eventually deployed with the army overseas – only to discover that something horrible has happened while she was away.

Lila is in the midst of committing a crime. Is what she’s doing “wrong”? Yes. But faced with the moral conundrum of letting Canada deliver its own form of justice or choosing her own, she reworks her army vows to chilling personal effect: “I have to carry through my pledge to serve and protect by doing everything I can to make the world right again.”

The theme of war – expecting it, preparing for it, enduring it – runs strong throughout Deer Woman. It is a subject that Beagan, a Ntlakapamux descendant, knows well.

In 1973, Beagan’s 12-year-old cousin was abducted, raped and left for dead in the mountains. Yet the (white) man who committed these crimes – and several others – was only convicted last year, 45 years after the fact.

‘Deer Woman is about feeling powerless and trying to take that power back’: Tara Beagan. Photograph: Article 11

The number of crimes committed against Indigenous women and girls in Canada is high, but convictions are rare (Indigenous women comprise 4% of Canada’s population but 16% of all female homicides). So Beagan was astonished that the man, who was initially questioned but released by police in the 70s, was eventually uncovered through a sting, found guilty and imprisoned.

“Did it feel good? It did in a way, because [the victim’s] mother was alive and able to see that person convicted and publicly shamed for what he did, when we all know of similar circumstances where [the accused] just walks,” says Beagan.

“This story, Deer Woman, is about feeling powerless and trying to take that power back. Writing it was what little I could do in response to inaction in this country, because I do feel like we’re at war. I don’t know anyone who hasn’t been affected by having our women and girls abducted, raped and killed: literally everyone is just one or two degrees of separation away from this reality.”

Blackfoot actor Cherish Violet Blood, who plays Lila, grew up on southern Alberta’s Blood reserve, the largest in Canada, spanning roughly 1,400 sq km. Racism and abuse from non-Natives against Blood, her family and friends were etched into daily life, she says: “We were treated bad from a young age and you just normalise it really early – ‘Oh, they just don’t like us’ – even though Canada likes to pretend it’s nice to everyone.

“Growing up through all that racism, and then getting into the business of being a performer and actress and always having to play the ‘victim’, this is probably the first role where I’m not being raped or fucked up somehow – so, to me, that is empowering.”

Other plays about the violence faced by Canada’s Indigenous women have made headlines in recent years, but not always for positive reasons. In perhaps the most notable, Pig Girl – based on the 2007 case of serial killer Robert Pickton, who is believed to have murdered dozens of Indigenous women at his Vancouver pig farm – a character is hauled up on a meat hook and sexually assaulted before the audience. The play was written by a non-Indigenous playwright and won prestigious awards.

Beagan wrote Deer Woman partly in order to reclaim her own power as a playwright. Her intention, she says, was to rewrite the “Native” story too often pushed by “settler” narratives.

“Some artists in Canada have privileged themselves to tell the stories of some of our missing and murdered Indigenous women and girls, and I consider that poaching, frankly,” says Beagan.

“It’s taking very real trauma, very real atrocities already largely perpetrated by settler society in Canada, and allowing such society to profit from it. I find it sickening. You can’t take our lives and our stories, too.”

Cherish Violet Blood in action as Lila in a performance of Deer Woman at this year’s Sydney festival. Photograph: Prudence Upton

Deer Woman, which plays at Edinburgh’s fringe festival this week, premiered last summer at New Zealand’s Kia Mau festival and in January took the Sydney festival by storm, critics hailing it as “painfully real” and “a work of immense power and restraint”.

Audiences at the play’s European premiere are expected to hail from the “settler” side rather than the Indigenous side, says Beagan. Nevertheless, festival-goers are more than likely to be able to relate to the theme of powerlessness present in the story, thanks to “how many totally wacky leaders exist in the world right now, and how little power people feel they have about that”.

As yet, however, no dates have been scheduled in Canada , where both Beagan and Blood feel a serious self-reckoning needs to take place.

“Canada has a real problem. We have thousands and thousands of missing and murdered women and girls, and they’re all Native,” says Blood.

“Is it possible to not be angry? No. But it is possible to work from a place that is not anger. Either I do this [play] and do my best getting this message out to people without getting arrested, or I become some kind of wicked vigilante and take matters into my own hands.”

Deer Woman, part of Indigenous Contemporary Scene, will be at CanadaHub at the Edinburgh fringe, from 31 July to 24 August