Then came screams. Margaret was never seen alive again.

It was the 1970s on the Gold Coast and hitchhiking was common, particularly among the young surfie set.

Even the girls ‘hitched’. It was a free and easy way to travel up and down the Gold Coast Highway - to the beach, a mate’s party or the pubs and clubs from Surfers Paradise to Coolangatta.

Short of cash to see a band at The Playroom or The Cabbage Patch? Not a problem - just thumb a ride.

“Where ya’ groin? Yeah, no worries, jump in.’’

Hitchhiking was part and parcel of the laid-back Gold Coast lifestyle that free-spirited Margaret loved.

She’d moved out of her parents’ home on Chevron Island and was living with friends in a flat on Old Burleigh Rd in Surfers.

She worked in a fish and chip shop. Liked to go to the beach, hang out with her mates and smoke a bit of pot.

“She didn’t take things too seriously and had no driving ambition,’’ her little sister and ‘best friend’ Brenda Atkinson recalled in a 2011 interview.

“She was happy to work and live her life.’’

May 5, 1976 was a party night. A farewell for one of Margaret’s mates.

The shindig was down at Burleigh Heads, 15kms or so from Surfers.

It was 9pm but that didn’t worry Margaret. Hitchhiking was second-nature, even after dark.

“I never hitchhiked but I knew Marg did — back then it wasn’t unusual,’’ Ms Atkinson said.

Margaret never made the party.

Brenda was in her first year of university at Toowoomba when she got a call from their parents asking her to come home. They didn’t tell her why.

“When I walked in the door I remember having a really uneasy feeling,’’ Brenda said.

“I asked my parents where Marg was and they told me she’d vanished. It just got worse from there.’’

It was 16 days before Margaret’s battered body was found.

A couple looking to buy an overgrown block of land on Newcastle St, West Burleigh, stumbled across the remains.

Margaret’s denim dress had been torn from her body and her underpants were missing.

Police described her murder as ‘the work of a sadistic fiend’. Her forehead was pulped and her jaw broken. She could only be positively identified using dental records.

Coins were found on the road about 10m from Margaret’s body, hinting a struggle may have taken place near a car.

While police initially believed she was killed on the same night she disappeared, they later theorised that she may have been held captive for several days.

They based this theory on screams witnesses reported hearing after her abduction, and on the discovery of Margaret’s empty handbag in a gutter near Broadbeach Surf Club two days after she went missing. The area is cleaned daily, suggesting the bag may have been dumped there.

A crime scene examination yielded few clues to the grisly murder.

“There had been heavy rain and we just couldn’t find much at all,’’ retired forensics officer Neil Raward recalled.

“We found no shoe prints, no footprints — nothing of much significance at all. It had been very brutal but there wasn’t much to go on.’’

Police at the time believed Margaret could have been the victim of a possible serial killer dubbed ‘The Hitchhiker Murderer’ who may have killed as many as seven young women on Queensland roads in the early to mid 1970s.

They included Gabriele Jahnke, 18, and Michelle Riley, 16, who were hitchhiking between Brisbane and the Gold Coast in 1973 when they were murdered.

Both were found bludgeoned to death. There were also signs of sexual assault.

Police even compared the skull injuries of Margaret and Gabriel Jahnke.

“All three girls died from massive head injuries, all had been hitchhiking and all the murders tie in geographically,’’ said former acting Police Commissioner Ron Redmond, who investigated the Margaret Rosewarne slaying as a Homicide Squad detective.

Of Margaret’s slaying, he added: “This is a vicious and brutal attacker. We think he knows the Gold Coast area very well.’’

While Margaret’s murder happened two decades before Ivan Milat’s reign of terror, her family called for possible links to the ‘Backpacker Killer’ to be investigated.

“I don’t think enough has been done,’’ Margaret’s brother Paul Rosewarne said three years ago.

“I thought they’d be able to do DNA. I don’t understand why the police have ruled out Milat.’’

Brenda Atkinson agreed: “It’s the kind of scenario that could fit the profile of Ivan Milat.’’

Police, however, believe Milat was in New Zealand when Margaret was murdered.

Her family was also upset at police suggestions her slaying may been linked to drugs.

“All the initial investigations revolved around drugs, but it seemed so ridiculous to everyone,’’ Brenda said.

“It was the Gold Coast and it was the 1970s, so everyone was dabbling with pot. Marg smoked pot too, but it was a social thing. It seemed like the only line the police wanted to follow and it made no sense.

“To begin with, the police didn’t take Marg’s disappearance seriously. They seemed to think she’d just gone off somewhere for a few days. But it wasn’t like Margaret to go away and not tell anyone.’’

Almost four decades on, Margaret’s murder remains unsolved.

Not even a $250,000 reward could elicit critical clues needed for an arrest.

The ‘Hitchhiker Murderer’ has never been caught.

“Sometimes, you flip between wanting to know the answers, then wondering if you want to know because it’s been such a long time,’’ her sister said.

“I think, when it comes down to it, we need to know what happened. It has to be solved in some way.

“My parents always had a huge amount of faith that the police would find out who murdered Marg, but they died not knowing.’’

In 1980, after a spate of hitchhiker murders, the State Government decided something had to be done.

“There have been a number of instances where young persons who have hitchhiked on roads have been given a ride and subsequently murdered,’’ Police Minister Russ Hinze and Transport Minister Ken Tomkins told Parliament in a submission.

“Tragically, many young people — confident of their own invulnerability — will continue to hitchhike no matter how appalling the risks.’’

State Cabinet approved a $20 on-the-spot fine for hitchhiking.

It came too late to save Margaret Rosewarne, the last known victim of the ‘Hitchiker Murderer’ — if indeed there was a single serial killer.

“Marg was someone who had a really loving spirit. She was so naive and trusting,’’ Brenda Atkinson said.

“Marg was a trusting person and, in the end, that’s what led to her murder.’’

Call Crime Stoppers on 1800 333 000.