Echoing down a tinny line from a phone box in Brisbane to a farm outside Dubbo, 20-year-old Lorraine Wilson could not hide her exasperation with mother Betty.

It was October 1974. Gough Whitlam was in power, Sherbet was on the radio and spring was in the air. Lorraine and her best friend, 18-year-old Wendy Evans, had finished their first-year nursing exams at Sydney's busy St George Hospital, and were embracing independence and freedom that women a generation earlier could barely have imagined.

After a bus tour up the east coast to Townsville, and then across to the Northern Territory, the two girls had returned to the Wilsons' rural NSW property for a few days of relaxation before heading north again, this time in Lorraine's 1964 Volkswagen Beetle. The pair intended to drive back through Brisbane and the Gold Coast, where they hoped to work on their tans before returning to work on October 10.

They would never make it. The last time Betty Wilson would see her youngest child - the tomboy whose cheeky laugh belied a caring nature - was in a cloud of dust on September 30, as her little Bug bounced down their dirt drive. The last time they would speak would be a few days later, when Lorraine called from a Brisbane payphone. It turned out the car had broken down on the NSW-Queensland border within hours of the girls leaving, and been towed into Goondiwindi. The girls had then hitchhiked 350 kilometres back to Brisbane, where they were staying with Wendy's older sister, Susan Vlismas, at Camp Hill, on the city's south side.

Lorraine told her mother she and Wendy were considering hitching back to "Goondi" to collect the car, as time was rapidly running out on their leave. Both Susan and Betty separately begged the girls not to take the risk. Betty suggested she and husband Eric snr could drive up to collect the car, while Susan offered a loan to cover the bus fares, reminding them of the chilling double murder of teenagers Gabrielle Jahnke and Michelle Riley a year earlier. The girls had gone missing while hitchhiking from the Gold Coast to Brisbane, their bodies found dumped in two separate locations. Both had been raped and savagely bludgeoned to death. But high on the energy of their holiday, the friends could not be swayed.

"I've got Lorraine to protect me - she's a judo expert!" Wendy exclaimed, prompting both girls to dissolve into fits of giggles. Although she was relatively tall at 167 centimetres, and fit from years helping out on the farm, Lorraine was no martial arts aficionado. But she reassured Susan: "There's nothing to worry about as long as you're sure about the driver."

Late on the morning of Sunday, October 6, the nurses set out on foot from Susan's house, each lugging a small vinyl suitcase and heading for the main road, more adventures - and the unknown.

About 800 kilometres further south, as she strode across a paddock three days later, Betty was felled by a sudden, stabbing pain that made her clutch at her heart. "Oh Lorraine!" the family matriarch cried out, without really knowing why. "I hope you're safe!"

It's the not knowing that messes with your head. A haunted intensity blazes in Eric Wilson jnr's eyes as he struggles to explain why, after almost 40 years, he is still pursuing details about the grim fate that awaited his sister on that promising spring day.

It was Eric jnr, Lorraine's closest sibling, the one who used to drive "the little scallywag" around in his home-made billycart to collect eggs from the chickens, who called St George Hospital at his mother's behest on October 12, 1974, only to learn that the girls had never arrived back for their first shifts. And Eric, too, who packed up his wife and their newborn daughter and moved back from Sydney to support his parents as they waited for news, and eventually to run the farm while Betty and Eric snr travelled up and down the east coast with photographs of their missing child.

Even now, his eyes cloud as he remembers the painful unravelling of days, then weeks, and finally months with no real news from police, and the weight of fear and grief slowly crushing two people bred from the toughest stock Australia has known: his fearless father, a World War II veteran, and his formidable mother, who could have stepped straight from the pages of Henry Lawson's The Drover's Wife, or off the canvas of the Russell Drysdale painting.

"I think we knew right from the word go that something was terribly, tragically wrong, that Lorraine wasn't coming home," the 62-year-old nurseryman says now. "But Mum wasn't like that. She was going to hang on for her. Months later, coming up to July [1975], it would have been Lorraine's 21st birthday and Mum insisted on baking and icing a cake. Just in case Lorraine came home unexpectedly for her birthday, she wanted to have that cake ready."

By then, Betty had become a virtual recluse, refusing to travel further than a few hundred metres from the homestead - closer, if she was the only one there - lest Lorraine somehow free herself from whatever strife or evil had overtaken her, and was able to phone home. But then, when the phone rang on June 30, 1976 - almost 21 months after the girls were last seen by Susan Vlismas - it crushed all remaining hope.

The day before, an older couple out on a date in the foothills of the Great Dividing Range had turned off Murphys Creek Road, about 30 kilometres down the range from Toowoomba, and eventually onto an unsealed track. Bushwalking through the scrub, they had stumbled upon a remote clearing, scattered with personal belongings and, horribly, what appeared to be the remains of two human beings, five or seven metres apart, hogtied with cord. When police arrived at the scene, one of the first items found at the site was a transistor radio, inscribed with the name "Lorraine Wilson".

"I remember Dad coming across the paddock to meet us as we headed from our cottage to their house with the baby," says Eric, "and I knew before he said a word. He had that 'thousand-yard stare' that soldiers get when they have seen too many awful things. He just wasn't there any more. Something had broken inside him ... and he was never the same again."

Nor were the rest of the family. As they said their goodbyes to Lorraine and interred her ashes, Eric and his older brother Doug vowed: "We'll get the mongrels who did this." But eventually, Doug insisted that he could not spend his life searching for pieces of a jigsaw when the final picture was always going to be one of brutality and despair. Others, too, simply shut down the painful memories.

But as the years rolled into a decade - an inquest in 1985 ended inconclusively, determining only that the girls had met with "foul play" - Betty and her younger son found their need for answers grew ever stronger.

"I was tormented by it," says Eric. "I just wanted to know the stepping stones of the events. It's hard to accept that we might never, ever find out. The thing is, you compound it every day. It makes it worse in your mind, if that's possible - all those unanswered questions, the not knowing. You walk around every day with a mountain of fear sitting on your shoulder."

This year, a second inquest, prompted in part by the Wilson family's relentless pursuit of the truth, raised more disturbing questions about a subculture of violence, serial rape and lawlessness that apparently flourished unchallenged in Toowoomba, otherwise known as "the City of Flowers". How was this possible? Why had up to 10 people turned their backs on Lorraine Wilson and Wendy Evans on the night of October 6, 1974, refusing to intervene or call police, as the two terrified girls screamed and begged for help? And, with bystanders turning their backs on her, had Wilson's fate been sealed by her own act of courageous loyalty, when she escaped from her assailants only to return to their car because she refused to abandon her best friend?

Sometimes, in the dead of night particularly, the questions of a brother and of a mother become more personal. Were you frightened, Lorraine? Did you suffer for long? Will you forgive me for reassuring you that the car was roadworthy, for not insisting you come home on the bus straight away, for not protecting you somehow?

And on a cold, grey day outside the Brisbane Coroners Court in June of this year, during the second inquest that he and Betty had fought so hard for, Eric Wilson reveals that he is plagued by one further question: "Do you think I'm crazy to have pursued this for 39 years?"

In April last year, Betty Wilson sat down to write a three-page letter in her painstaking cursive script to the Queensland state coroner, Michael Barnes, who forwarded it to Jarrod Bleijie, the newly appointed attorney-general of the state's incoming Liberal National Party government.

"It is a practical reality that this will be the last investigation [into] my daughter Lorraine's case in my lifetime," the 86-year-old wrote, after detailing some of the new evidence that had been flushed out since the first inquest. A slew of new witnesses had come forward in the wake of a television reconstruction of the case on Australia's Most Wanted in the late 1980s, and even more after the publication of The Echo of Silent Screams, Eric Wilson jnr's own book about the case, in 2003.

Betty was characteristically blunt, even fearless, stating plainly that she now believed she knew the identities of her daughter's assailants, including two men, one deceased and one still alive, who could have been charged with murder. "I wish to rest in peace and I urge, for the sake of the girls, who do not have a voice, as well as for my own, for you to convene a [second] coronial inquest."

By then, Betty and Eric had renewed hope. In 2003, impressed by Eric's persistence and the detailed research that had gone into The Echo of Silent Screams, Queensland Police Assistant Commissioner Mike Condon had promised to put the police's "best man" on the job. He handed responsibility for the cold case to Detective Inspector Kerry Johnson, a former homicide squad member who had gained a reputation for his clean-up rates.

Eric Wilson was not going to let the opportunity pass. "Kerry could have had me prosecuted for stalking," he says ruefully. "I rang that man every Friday for almost 10 years and asked him what he'd done about my sister. There were times when I knew he had other things on, but I just wouldn't let it go."

But three days after writing her letter, Betty suffered a freak accident, slipping and severing an artery while working alone in the garden. She did not live to see what her unfaltering faith and Eric's dedication had prompted: after almost four decades of false hope and relative inaction, the wheels of justice began to turn. By September of last year, Bleijie had heard the arguments and directed a second inquest be convened.

At a pre-inquest conference in December, seven "persons of interest" were publicly identified for the first time: Allan John "Shorty" Laurie, Donald "Donny" Laurie, Wayne "Boogie" Hilton and Larry Charles, all of whom had since died, and Desmond "Dessie" Roy Hilton, Allan Neil "Ungie" Laurie and Terrance James "Jimmy" O'Neill, who were directed to appear before the court to give evidence.

The names gave the first hint of the chilling revelations to come: that several young men drawn mainly from two extended families, entangled over several decades by intermarriage and mutual dealings, had run rampant through Toowoomba and its environs during the 1970s, establishing a fearsome reputation for sexual assaults and indiscriminate violence.

The publicity drew out more witnesses, and when the inquest finally opened this April, their testimony would often conjure comparisons with Deliverance, the 1972 film in which four friends become lost in the backwoods of Georgia and are terrorised, sexually and physically, by a group of inbred hillbillies.

"They'd get you in the car and offer you a lift home - but you would never get home," one protected witness, "Gail", said in a statement to the inquest. "When you got in the car there were no door handles inside or window winders ... That's why we couldn't get out of the car. I don't know why they would rape me ... they took turns."

Another victim, "Kerry-Ann", said the Hilton and Laurie gangs were known for snatching women off the street, sometimes throwing them into the boot of the car, and taking them to regular overnight parties convened in a dry riverbed near Goondiwindi: "I was just brutally bashed by whatever those thugs could use on me and repeatedly raped by all of them."

The alleged perpetrators' own families were not immune. One member of the group was reported to have "knock[ed] down his mother by punching her head and stomping on her", while Wayne "Boogie" Hilton's ex-wife Roylene had previously submitted a statement that "whenever he wanted sex he would just take it whether I consented or not. I resisted him on some occasions but he just punched me up and held me down and forced me into sex."

Like most groups of bullies, this one was ultimately exposed, partly because of its members' propensity to brag about their crimes, as well as their inherent cowardice when singled out from the crowd, and their lack of real loyalty to one another.

Boogie's uncle, Trevor Hilton, told the inquest: "Everybody in the town knew what they were doing. I don't know why it wasn't stopped in them days because then those nurses probably would still be alive."

Interviewed by Johnson in 2008, Desmond Roy Hilton, 63, said "Shorty" Laurie, "Ungie" Laurie, Larry Charles and Jimmy O'Neill had turned up the morning after the murder occurred, boasting about how they had "given two girls a hiding down the bottom of the range ... I took that to mean that they had done to the girls what they had done every weekend for a number of years; that is, taken somebody out, given them a hiding, raped them, and then when they had got what they wanted off them just left them there."

Although he insisted under questioning during the inquest that he couldn't remember making the earlier statements, Hilton had also told Johnson previously that "Shorty" had made him clean blood out of his EJ Holden that morning and had demonstrated later how he kicked and stomped on the girls. (Police had earlier considered charging Des Hilton as an accessory to murder.)

A former sawmill manager, Neil Shum, told police in 1989 that "Boogie" Hilton had confided several times while working at the mill that "he and someone else killed two nurses down the range", but Shum hadn't believed him because he thought it was "just piss talking or Wayne bullshitting".

But why did police fail to even question members of the Hilton/Laurie clan, given their local notoriety, when the nurses' bodies were discovered in 1976? Kerry Johnson is circumspect, stressing that he doesn't see any value in "pointing fingers" at earlier policing methods, particularly from an era that preceded computerised databases and modern forensics.

Early investigations were also thrown off-course by the mistaken assumption the murders were linked to the Gold Coast hitchhiker killings. Meanwhile, many of the Hilton and Laurie men had also left town, ostensibly to chase manual labouring jobs elsewhere, long before the crime scene was revealed. "And whether it was because they didn't think they would be believed, or because they thought they would be blamed for getting into trouble, you have to remember most of those local girls never reported what happened to them," Johnson says.

But it is one thing to imagine intimidated locals enduring the overbearing violence of a group of local thugs - or, as coroner Michael Barnes branded the Hilton/Laurie gang, "a putrid pool of miscreants". It is another entirely for utterly decent people to hesitate, and even turn a blind eye, when confronted with the spectacle of two young women pleading for their lives.

But that is, apparently, what happened as darkness fell on the "City of Flowers" that night. Norma Sperling was preparing dinner at her home near the Toowoomba Range Road when she heard a voice call out near the back door, and discovered a young woman standing in her laundry. "Can I stay here for a while?" the stranger had asked, explaining that she "wanted to get away from some people". Sperling was taken aback and offered to call the police, but the young woman declined.

According to her police statement, Sperling then replied: "You can't stop here." Instead, she suggested the young woman leave via the back garden if she didn't want to be detected.

"They'll probably still find me anyway," the stranger replied. But she left.

Minutes later, Sperling heard a scream from the front of the house. From a window, she saw a man hitting the young woman across the face as he tried to force her into a car, where another woman and man were already struggling in the back seat. Sperling said she again considered calling the police but her husband, arriving home soon afterwards, told her not to get involved because it "was probably just a domestic".

It was not until 1989 that Sperling would tell police of the incident, using photographs to identify Wilson as the young woman who had asked to hide in her laundry, and "Boogie" Hilton as the driver of the car.

Heartbreakingly, even this was not the girls' last thwarted chance for rescue. Over the years, no fewer than 10 witnesses have come forward with accounts of seeing one or two women fighting off men along the steep and treacherous Toowoomba Range Road at that time. But none stopped to intervene and there are no police records to show that anyone reported an incident that night (although one couple has disputed this, insisting they did speak to officers at nearby Helidon).

At the inquest, Bryan Britcher fought tears as he described how his headlights had revealed a distressing scene that night: one woman being held around the throat next to a parked car, while about 20 metres further along, another woman was being frogmarched back to the vehicle. "Help us, oh God, help us!" they were screaming.

With his wife and young daughter in the car, Britcher said he was too scared to stop "and I've lived with that for 38 years". When the girls' bodies were discovered, the Britchers went to police.

Almost 30 years later, Vivian and Rose Murphy came forward to reveal that they, too, had witnessed a woman crying for help as she was chased down the same road by a man, while another couple appeared to be "cuddling" further away. "As I looked through the rear side-passenger window, I could see that the man had grabbed hold of her from behind," Rose Murphy told police. "I felt instant fear for her and my children [asleep in the back of the car], and I turned to Viv and yelled: 'Don't stop! Keep driving!' "

Coroner Barnes received testimony from six more witnesses whose various recollections all shared some common details: that there had been either one or two women engaged in a struggle with one or two men, near an early-model Holden pulled up on the left side of the Toowoomba Range Road. In one account, the women were tied up; another described a man with a prominent tattoo similar to one sported by "Boogie" Hilton; a number of eyewitnesses later identified Lorraine Wilson and Wendy Evans as the women they saw that night.

"Their desperate cries for help that went unheeded are one of the most heart-rending aspects of this terribly sad case," Barnes noted. "With the failure of these people to even attempt to intervene went the girls' last chance of survival."

What happened in their final hours remains uncertain, amid obfuscation and claims of lost memories by some key witnesses, and blatant and contradictory evidence by others who were accused before the court of simply chasing media attention. But Barnes placed particular emphasis on a detailed account given by Toowoomba resident Kim Sandercock in 1989, because it included accurate descriptions of the nurses' injuries which had never been publicly released by police.

Autopsies showed that Lorraine Wilson and Wendy Evans had suffered distinctly different, but fatal, head traumas. Wilson's skull had been fractured on the left side, by one to three blows. However, Evans had suffered multiple, severe fractures to her face, the top of her head and both sides of the skull, indicating she had been beaten beyond what it would have taken to kill her. Her face would literally have been "bashed to a pulp", a pathologist who attended the scene concluded.

In her 1989 statement, Sandercock had told police she had met a woman four years earlier at a local pub who had confided she had been with Allan Laurie and "one of the Hilton boys" when they picked up two nurses and later murdered them. "The men thought the women were prick teasers and were going to do something to them to teach them a lesson," Sandercock said. "They were going to play some sort of game with them and rape them. Murder was not the intention."

But as they travelled to Murphys Creek, the driver had slapped and pulled the hair of the nurse travelling in the front, prompting her to try to escape from the car. At that point, the man in the back seat had hit her in the head with an iron bar, causing her to slump forward, bleeding profusely. The second nurse began to scream; the decision was quickly made that both would have to be killed.

Sandercock claimed that the mystery woman said the second nurse escaped from the men when they pulled off the road in a remote clearing. "They bashed her head in," she said. "They did her worse than the first because she was the one giving them all the trouble."

But called to give evidence at the inquest, Sandercock arrived in a wheelchair, hooked to what she said was a morphine drip and insisting her use of analgesics had destroyed her memory. Barnes reserved his frustration for his findings, when he accused Sandercock of concocting the mystery female witness and lying about her own poor memory to hide what she knew "either because she fears retribution or inculpation".

"It is far more likely Ms Sandercock was either herself present ... or a person relayed the story to Ms Sandercock and is known to her and repeated it more than once," the coroner said.

In his findings, Barnes determined that Lorraine Wilson and Wendy Evans were the tragic victims of an attack "mounted to satiate the perverse sexual dysfunction of a despicable gang of thugs" associated with the Hilton/Laurie clan. The coroner found there was enough material for Wayne Robert Hilton to stand trial in relation to their deaths, had he not been killed in a car accident in the mid-1980s. But short of further evidence, "Boogie" Hilton's surviving accomplices will also go to their graves untried.

A week after the conclusion of the inquest in June, Eric Wilson sounds like a different man. It's as if 39 years and a lifetime of longing have fallen away.

While he concedes that he is disappointed that no charges have been recommended by the coroner, he says he is deeply satisfied that his sister's ordeal has not been wiped from history, and that the community is now aware of the monsters walking free among them. "The mountain of fear that sat on my shoulders can sit on theirs now," he says.

And while some questions remain about what happened that night, Wilson has many answers, including some that did not come from the witness box. "During the inquest, I went back to the site where the bodies were found," he tells me. "And it was a totally different feeling from the first time I went, when I could just feel Lorraine's presence there in the bush.

"She isn't there any more - and that's a good thing. She doesn't need to be. She's moved on."

This much more Eric Wilson knows: that he wasn't at all crazy to pursue justice for Lorraine for 39 years, after all. His mother Betty and his sister now rest in peace.

This article originally appeared in Good Weekend. Like Good Weekend on Facebook to get regular updates on upcoming stories and events.