In 1974, cousins Raelene Eaton and Yvonne Waters disappeared. 50 years later, the investigation is ongoing.

In 1974, Perth was a city basking in the glow of a mining boom. The beaches were packed every weekend, and Sunday sessions at beachside pubs were a ritual for young West Australians seeking sun, surf, and socialising.

But on April 7 that year, what started as an ordinary Sunday afternoon would become one of Western Australia's most enduring mysteries — one that would haunt families, baffle investigators, and remain unsolved for half a century.

The day Raelene Eaton and Yvonne Waters disappeared.

"Have a good time."

These were the last words Raelene Eaton's mother said to her daughter before she disappeared.

Raelene Eaton was 16 when she left the house to meet up with her cousin, 17 year old Yvonne Waters on April 7. They had told their families they were headed to the Oxford Hotel in Leederville to watch a band perform. But the cousins, who were also close friends, never made it home.

Police believe that at some point on April 7, Raelene and Yvonne decided to head to the White Sands Hotel in Scarborough. Witnesses at the White Sands that afternoon would later recall seeing the girls in conversation with three "scruffy" men who stood out from the usual crowd. The men were described as rough around the edges and in their early 20s — notably older than the two girls.

The last reported sighting of the cousins was outside the White Sands Hotel, where a witness reported seeing the girls outside the venue, talking to the men they had been socialising with. When the witness looked back up, the girls — and the men they had been with — were gone.

The initial investigation.

In the immediate aftermath of their disappearance, the police response reflected the prejudices of 1970s Australia. The girls' absence was initially dismissed as two teenagers taking off for "a good time" — a devastating blow to their families who knew something was terribly wrong.

For decades, investigators worked with incorrect information. They believed the girls had gone to see a band called Fatty Lumpkin perform that night.

However, music historian George Matzkov has recently discovered the band playing was actually called Orange. It's a seemingly small detail, but one that led police to question whether the cousins actually went to the pub to meet someone. In turn, it's led investigators to question what other details may not have been correct, and what else they don't know.

Watch the promo for 7NEWS Spotlight: Vanishing Cousins. Article continues below.

The latest clues.

Fifty years on, new information has breathed fresh life into the investigation. To date, two notorious Australian killers have been linked to the case.

Christopher Worrell, known for the Truro murders in South Australia, was stationed at Perth's Pearce air base during this period. According to crime author Geoff Plunkett, Worrell later confessed to his accomplice about abducting and murdering two women from Western Australia.

Queensland child killer Barrie John Watts has also been investigated, though police found the tip linking him to the disappearances "less than credible".

Detective Senior Constable Peter Shanahan, who has led a recent cold case review, believes the key to solving this mystery lies in understanding the relationship between the cousins and the three men from the pub. He has made a public appeal to these individuals, assuring them they would be treated as witnesses if they come forward.

Now, Channel 7 is putting the case back in the spotlight with a new special investigation titled Vanishing Cousins: Evil by the Beach. The promo for the special promises "shocking new clues" and details from new witnesses.

For now, what happened to Raelene and Yvonne on that autumn Sunday in 1974 remains a mystery. But for their families, who have lived with questions for half a century, these new developments offer a glimmer of hope that the truth about their loved ones' fate might finally be revealed.

Feature image: Australian Missing Persons Register.