On Australia Day, 26 January 1966, nine-year-old Jane, seven-year-old Arnna, and four-year-old Grant Beaumont vanished from a beach in Adelaide, sparking South Australia's largest search and rescue operation. Despite intense efforts, the children were never found. 

The disappearance captivated the nation, and six decades later, it remains one of Australia's most haunting mysteries, etched in the minds of everyone in Adelaide at the time. 

"This is one of the most examined cases in our history," says Adam.

"The police have worked hard, but even their own statement confirms that they're no closer to solving it." 

"There are different theories amongst even police. The reality is those theories, and theories put forward by others, are considered, but there remains no proof as to who is responsible," adds Steve.

Adam and Steve meticulously retrace the children's steps on the fateful day, uncovering new evidence and presenting their findings to former South Australia Supreme Court Justice John Sulan, for a fresh evaluation. 

The Beaumont children disappearance investigation features expert insights from co-authors of Unmasking the Killer of Missing Beaumont Children, Stuart Mullins and former SA Detective Bill Hayes; politician and former journalist Frank Pangallo; investigative journalist Graham Archer; former photojournalist Ken Sellick and forensic psychologist Deb Bennett. 

The Flinders Highway, an 800 kilometre stretch of road through Queensland's outback, has a dark and chilling history spanning over 50 years, with more than 12 people vanishing or being murdered between 1970 and 2018 – yet only one case has been solved.

In the gripping new investigation on The Hunters, airing this Sunday on Seven and 7plus, investigative journalist Adam Shand and former detective Steve Van Aperen embark on a road trip along this notorious highway of death. They revisit haunting cold cases, probing unsolved murders and disappearances, to uncover whether this isolated outback highway was a killing ground for Australia's most notorious serial killers.

The duo delves into three haunting cases, including the brutal murders of the Mackay sisters and Catherine Graham; the remains of all of them were discovered in Anthill Creek. They also investigate the disappearance of two young hitchhikers, Anita Cunningham and Robin Hoinville-Bartram, who vanished in 1972.

In July 1972, Anita and Robin set off from Melbourne to hitchhike to the latter's mother's house in Bowen, a journey they would never complete. Months later, Robin's remains were discovered in Sensible Creek, under a bridge on the Flinders Highway. The fate of Anita remains unknown to this day. 

The Hunters explores the landscape, profiles potential predators, and examines possible links between the crimes. Is this the work of one killer or multiple killers? 

Adam and Steve test claims that the crimes may have been committed by some of Australia's most infamous figures like Ivan Milat, convicted Whiskey Au Go Go murderer John Andrew Stuart and alleged child killer Arthur Stanley Brown. They also interview key witnesses and sources who possess crucial knowledge of these decades-old cold cases.

In a powerful moment, the team takes Anita's brother, David Cunningham, to the site where his sister's remains may be found after vanishing 50 years ago.

For the first time ever, the investigation reveals an eyewitness who spoke to Anita and Robin before their disappearance – and may have witnessed their final moments.

The special investigation features key insights from retired Queensland Police Detective Seargent Mick Gurn, retired Queensland Police Officer Brian Beveridge and forensic archaeologist Dr Louise Steding.