In Baltimore, Maryland, in 1969, a 26-year-old Catholic nun was murdered and her suspected killers, alleged abusers and paedophiles, left free to their continue their crimes.
Years later, a new seven-part Netflix series, the forthcoming The Keepers, has thrust the case into the public eye - and, judging by its gripping trailer, may have uncovered new evidence about a decades-old cover-up.
But the release of The Keepers is just the latest chapter in a long, ongoing story, which encompasses not just a murder, but a probable paedophilia ring, and deep-set corruption on the part of police force and church officials in Baltimore.
In 2015 The Huffington Post published an in-depth piece on the case, focusing on the stories of the former Catholic schoolgirls who came forwards, years later, to share their stories of the sexual abuse they endured at Archbishop Kenough High School, and their memories of the charismatic young teacher, Sister Catherine "Cathy" Cesnik, who promised to help them - and later ended up dead.
The key events from the case:
November 1969: Sister Cathy Cesnik disappears
Cesnik, a popular teacher at the all-girls Archbishop Kenough High School, disappeared after leaving the flat she shared with another nun, Sister Helen Russell Phillips, on November 7 1969. When she hadn't returned by 11pm, Phillips became concerned and called two priests, Father Gerald J. Koob and Father Peter McKeon, who later contacted the police. Cesnik's car was discovered nearby, parked illegally (and away from her usual spot).
Early 1970: Cesnik's body is discovered, but the police investigation goes cold
Cesnik's body was discovered in early 1970, and a forensic examination revealed that she had been choked, then killed by a blow from a blunt object.
Previously Nick Giangrasso, the detective looking into Cesnik's disappearance, had questioned Koob, after discovering a previous relationship between the priest and the young teacher. Letters between the pair revealed that their tryst had been called off after Cesnik took her vows as a nun, but that she had still harboured feelings for her former lover. Koob, however, had an alibi for the evening and night Cesnik disappeared.
After the discovery of the body, Giangrasso was forced to hand the case over to Baltimore County detectives, but later admitted that he had had some misgivings, suspecting that the Church was somehow involved, and that the police force consequently might not investigate the crime as thoroughly as they should.
"The Catholic Church had a lot of input into the police department," he later told the Huffington Post. "A lot of power."
Investigating detectives found no leads on Cesnik's death, and the investigation was later abandoned.
1992: abuse allegations throw new light on the case
In 1992, a woman named Jean Wehner came forward to claim that, while at Kenough, she had been abused by the school's chaplain, Father Joseph Maskell.
She initially turned to the local church authorities, who claimed that they were unable to find any evidence to support her case, before bringing in legal support. At the time, Maskell was working as a priest in Baltimore (he was briefly suspended during the Church investigation, then reinstated).
An appeal from Wehner's attorneys brought forward a number of former pupils with similar stories, one of whom, Teresa Lancaster, became the co-complainant in a civil lawsuit.
The women initially kept their identities hidden, fearing retribution, but later agreed to be named.
Early 90s: Wehner remembers being shown Cesnik's body
As well as recalling the abuse she had endured, Wehner also remembered being shown Cesnik's body by Maskell, months before the remains were officially discovered.
According to Wehner, in November 1969 the chaplain drove her to a secluded spot, showed her the maggot-covered corpse, and told her: "You see what happens when you say bad things about people?"
"He terrified me to the point that I would never open my mouth," she later told the Huffington Post.
The gruesome detail about the maggots later proved to be significant. At first, it shed doubt on Wehner's story: officials were unsure whether there would really have been maggots present so late in the year, due to the cold weather. But the autopsy results, which were not made public, showed that the creatures had indeed beenfound on the body.
1994-95: the case is thrown out, but police begin investigating Maskell
The allegations from Wehner, Lanacaster and several other women who had come forward painted a terrifying picture of fear and unchecked abuse at Kenough in the Sixties and Seventies.
Two other men, including Father Neil Magnus, director of Religious Studies at the school, and local gynaecologist Dr Christian Richter, were said to be involved in the sexual abuse, which targeted some of the school's more vulnerable pupils.
Three of the victims also recalled being forced to prostitute themselves to strangers, including, significantly, a number of uniformed police officers.
Their stories were horrific, but when Wehner and Lancaster attempted to bring a civil lawsuit against Maskell and the other abusers, the case ended up being thrown out of court.
At the time, there was a law that stated that civil lawsuits relating to sexual abuse had to be brought three years after the offence had taken place or discovered.
The Church brought in an expert to argue that it was not plausible that Wehner and Lancaster could not have repressed their memories of abuse for so long, only for them to resurface in the early Nineties.
But Wehner's testimony prompted a police investigation against Maskell - who promptly fled to Ireland, where he remained until his death in 2001.
Magnus had died in 1988, and Richter, who admitted that Maskell had sometimes accompanied his pupils into the room when they were undergoing exams but always denied having any part in the abuse, died in 2006.
In 2015 Sean Caine, a spokesman for the Archdiocese of Baltimore, told the Huffington Post that, in contrast to its previous position, the church now accepts that Maskell was "credibly accused of sexual abuse of minors".
2013: Gemma Hoskins and Abbie Schaub, two former pupils at Kenough, begin looking at the case again
Hoskins and Schaub were at school at the time of the alleged abuse, but were never targeted themselves, possibly because they were both confident, high-achieving pupils - unlikely to fall victim to a headmaster who reportedly preyed on the more insecure girls.
Hoskins had long been troubled by Cesnik's unsolved murder, however. After retiring from her work, she decided to throw herself into the long-abandoned investigation, contacting alumni from the school, and chasing up new leads.
Testimonies from the victims suggested that Cesnik, towards whom some of them had turned for help, may have been planning to expose the abusers.
One woman, who asked to remain anonymous, told the Huffington Post that she had been at Cesnik's apartment the night before she disappeared. While she was telling her about the abuse, a furious Maskell entered the flat.
"Maskell glared at me," the woman said. "He knew why I was there."
The next day, the woman said, Maskell threatened her with a gun, and told her he would kill her loved ones if she ever spoke up about what she had seen.
What else do I need to know about The Keepers?
Directed by documentary-maker Ryan White, The Keepers will tell the story of Hoskins and Schaub's investigation, looking at the new evidence the women have uncovered during the course of their work, and at the allegations of a police and church cover-up.
The series is already being compared to Netflix's 2015 true crime documentary Making A Murderer, which examined alleged police misconduct in the case of Steven Avery, a man who was wrongly convicted of sexual assault, released after 18 years after new DNA evidence came to light, then later arrested and convicted of a separate murder.
It also follows in the footsteps of crime documentaries such as The Jinx, which told the true story of suspected murderer Robert Durst - and sensationally captured a confession from Durst, leading to his arrest on murder charges.
All seven episodes will be available to stream on May 19.