There were also attempts to camouflage a trail of deadly secrets – hidden pieces of information that need to be placed under an investigative microscope.

It was 30 years ago on Friday that Allison, still a couple of weeks shy of her 18th birthday, walked out of the family home and into mystery which has enveloped her family and scarred large parts of a town.

A few days after she was last seen on October 6, 1993, Allison’s body was found under the sheets of iron on the disused garbage dump a few kilometres away at Pelton.

The cause of death remains unknown although homicide squad detectives have formally described her death as suspicious.

But what happened to her also remains unknown, with no one ever convicted over her death – a man was charged with concealing her body and perverting the course of justice after an inquest was terminated in 1994, but was acquitted in 1997.

Now, on the 30th anniversary of the day she left the family home and almost a year after the State Government announced a $750,000 reward for information leading to the arrest and conviction for those responsible for Alison’s death, comes a new plea for information.

The state’s homicide squad has confirmed that Allison’s death remained “actively under investigation” with investigators from the unsolved homicide team continuing to “examine every line of inquiry and search for answers”.

“Last year, we announced the monetary reward for information into her death increased to $750,000, and I want to remind the public that increased reward remains in place,” Det Insp Nigel Warren said on Friday.

“Thirty years on, we still believe there are people out there who know something, and we continue to urge anyone with any information – no matter how small – to come forward. Our investigators want to hear from you.”

The information are the secrets which have continued to torment Allison’s family over the last three decades.

Allison’s mother, Loretta, and sister, Sonia, made heartfelt pleas for information on Allison’s birthday last year.

“Sonia and I live this nightmare continually thinking what may have happened to Allison that night,” Loretta said at the time.

“Did she suffer, did she know who did this – these thoughts are forever in our minds.

“We really need somebody to be held accountable for doing this to Allison and for the heartache, grief and anguish we as a family have had to endure for the last 29 years.”

They described Allison as a happy, caring and trusting young woman who had finished study and was ready to begin the next stage of her life when she headed to that cafe and disappeared.

She loved a joke, she enjoyed spending time with family and friends, loved children and had recently finished study.

“Not a day goes by that we don‘t think of Allison and wonder if we will ever know what happened to her the night she was taken from us,” Sonia said.

“Because of the heartless way Allison had been hidden in bushland we were unable to see her to say our final goodbyes and cause of death has never been determined.

“Our father and other family members have passed away without knowing how Allison died and mum, myself and families need answers.

“We will never give up the fight to ensure the person responsible are held accountable for their actions.

“The people responsible have continued to live their lives without any remorse while we continue to suffer every single day.”

Homicide squad commander, Detective Superintendent Danny Doherty, said last year that it was hoped the increase would “incentivise” anyone who may have held onto information since Allison’s death, to come forward.

“Allison’s naked body was found underneath sheets of corrugated iron and physical evidence at the scene suggests that she was likely dragged to that location,” Det Supt Doherty said.

“Investigators do believe there are still people out there – particularly associates of Allison from the time – who have not yet spoken to police and may have useful information.