This gripping account of the abuse of First Nations children at Catholic residential schools in Canada rightly won the jury prize for documentary direction at Sundance in January and is now an early Academy Award favourite.

Early in the film, a group of volunteers ventures into a barn on the grounds of St Joseph’s Mission residential school near the Sugarcane Reservation in British Columbia. They find heartbreaking inscriptions from desperate children. Investigators Charlene Belleau and Whitney Spearing uncover more than 50 unmarked graves nearby.

Founded in the late 19th century, St Joseph’s was one of many state-supported Catholic institutions intended to counter “the Indian problem”. The grandmother of Julian Brave NoiseCat, the film’s codirector, who was himself born in mysterious circumstances in the institution, says, “Before we went to residential school we spoke the Secwépemc language – only Secwepemctsín – in the community; no English. They tried to take that out of us. So much stuff … stuff I should have talked about.”

The cruelty of assimilation is compounded by systemic physical and sexual abuse. Priests fathered children with girls in their charge. One survivor, Larry Emile, saw nuns dispose of an unwanted baby in an incinerator. Countless children ran away or died by suicide.

Rosalin Sam, an elderly survivor, recounts the culture of silence as she names the priest who abused her. “I went to the nun. She told me to tell the priest. I told the priest. He told me to tell the Indian agent. I told the Indian agent. He told me to tell the RCMP [Royal Canadian Mounted Police]. I told the RCMP. He went and told my dad. And my dad beat the s**t out of me.”

Headlines about the gruesome discovery of 200 unmarked graves of indigenous children at another regional school precipitate a series of arson attacks. Touchingly, a St Joseph’s survivor named Rick Gilbert, a devout Catholic and former chief, works to protect religious icons. A DNA test reveals he is 50 per cent Irish, fathered by one of the priests who were moved around institutions for “Eskimo and indigenous” children. Gilbert is invited to the Vatican, where Pope Francis asks for forgiveness. The damaged, rising community depicted in Sugarland are in no mood for apologies. They want accountability.

Sugarcane is on limited release from Friday, September 20th