Despite four police investigations over four decades and intense media interest into the sudden and mysterious disappearance Northern Beaches teen Trudie Adams — we are still none the wiser as to what happened to her on June 25, 1978.

It was that night she went to a party at the Newport Surf Lifesaving Club, asking her mum, Connie, to stay up for her. But the 18-year-old never came home.

After an argument with her ex-boyfriend, Steven Norris, she planned to hitchhike home — which wasn’t uncommon in the area at the time and it was only a five-minute trip to her parent’s house.

Just after midnight Mr Norris saw her get into a car on Barrenjoey Road and nobody ever saw her again. Mr Norris is not suspected of any involvement in Adams’ disappearance.

The hunt for her was the largest manhunt in NSW history at the time, but her body was never found and missing persons file remains open to this day.

More than 40 years later, the strange case has been thrust back into the spotlight.

Serious questions about the original police investigation, a disturbing series of violent rapes in the same area and alleged police corruption have been asked by award-winning ABC journalist Ruby Jones and investigative reporter Neil Mercer.

This week, the final part of their incredible true crime three-part miniseries into the suspected murder, Barrenjoey Road, hit screens and it revealed a sordid underbelly of the idyllic beach communities in Sydney’s north.

Ms Jones’ believes the case points to something much bigger — saying it shows how violence towards women was simply swept under the carpet and it was a tough pill to swallow.

“The last 10 months have been a confronting journey for all of us,” the filmmakers said in a statement. “Slowly, unevenly, we have come to know something of Trudie Adams and understand the sense of loss still felt by her family, friends and community. Adams’s liveliness, hopes and sense of humour underline the tragedy of her suspected murder as well as the failure to find and punish those responsible.”

They claim the “almost certain” murder of Ms Adams is linked to a series of unsolved rapes around Sydney’s Northern Beaches at the same time.

When the filmmakers delved in to NSW State Library they found that two men — often wearing disguises such as cheap plastic wigs, dark glasses and fake beards — were trawling up and down the same stretch of road for years looking for young girls.

They abducted 14 girls — all aged in their teens — at gunpoint and forced them into a car.

The victims were then taken to bushland, forced onto a mattress, forced to undress and the victims as young as 14 were repeatedly raped while the men sometimes took polaroid photos.

They got the victims’ addresses out of their purses, said they knew where they lived and made threats that they’d be killed if they told anyone.

“They would do the same thing over and over again. It was obviously something they’d nailed down as some sort of ritual that they did together,” said Ms Jones in the documentary.

“It seems like it was some sort of sick game really. It was almost like sport. They drove around the roads of Avalon and Newport looking for prey.”

Ms Jones said the 14 rapes were “shocking and very similar” and became progressively more violent leading up to Ms Adams’ disappearance.

Some of these victims identified a convicted drug dealer and sex offender called Neville Tween — also known as John Anderson — as one of the attackers.

He had also been the prime suspect in the case in the Ms Adams’ case, but he was never asked a single question about it until 2009.

Disturbingly, Tween was picked up with false beards, guns and disguises and was jailed for a disturbing bushland sexual attack on a young male pot dealer who sold him bag of weed which was mixed with grass.

Tween — who died in jail in 2013 — had always denied anything to do with Ms Adams.

When interviewed by police 2009 as part of the cold case investigation, he said the accusations linking him her disappearance were “all speculation” and there was no evidence to back them up.

Members of another group, from Sydney’s west, allegedly talked of their involvement in the infamous abduction, but, again, they denied this upon further questioning

Ms Jones and Mr Mercer delve head-on into the drug and corruption-riddled world of the 1970s Northern Beaches community.

“There was a dark underside to this very picturesque part of Sydney,” said Mr Mercer.

Earlier in the series, they looked at theory — believed by Ms Adams’ mother — that the popular teen, who was planning a trip to Bali, was being eyed up for a drug mule operation by local dealers.

However, Ms Adams’ childhood friends, Leanne Weir and Anita Starkey, told the documentary makers they categorically denied she had anything to do with drugs.

Ms Jones and Mr Mercer came to the conclusion that the drug mule theory had been debunked.

They even traced Ms Adams’ ex-boyfriend Mr Norris to his northern NSW home and spoke to him about what happened that night.

Ms Adams’ had recently broken up with her, then 22-year-old, boyfriend who is the last person known to see her alive.

He told police he saw her climb into a fawn panel van at 12.30am after she’d left the surf lifesaving club and walked towards Barrenjoey Road.

When her mother Connie reported her daughter missing to police she was seen getting into a green kombi van by Mr Norris.

Mr Norris openly spoke with Ms Jones and Mr Mercer in Barrenjoey Road saying he didn’t know how that information had been conveyed to Connie.

In the final episode — which is available on iview — they hone in on Tween and his “disturbingly close” and “unholy” relationship” with high-ranking and influential cop friend Mark Standen who Ms Jones claims was one on the “most senior and corrupt cops in the country”.

Standen was arrested in 2008 and later jailed for conspiring to import 300 kilograms of pseudoephedrine.

It is claimed they would go on family trips together to the Central Coast.

Barrenjoey Road is a compelling and frustrating look into how this incredible case has never been solved.

And although it will make your blood boil and chill you to the bone, the filmmakers hope it will finally help shake loose a new piece of evidence which could help us find out what happened to the bubbly blonde teen.

Watch it now, by clicking here.

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