It’s been more than four decades since Daryl Floyd’s brother went missing - but he says he’ll never give up on finding him.

The 52-year-old has spent the past eight years tirelessly searching an abandoned mine shaft in rural Victoria for what he believes is his brother’s final resting place - and has vowed to spend the rest of his life digging.

“Digging for Answers” airs this Sunday on 60 Minutes. For more on 60 Minutes, visit 9Now

“This is basically where all our information leads us to,” Mr Floyd told 60 Minutes reporter Tom Steinfort.

“And I believe he is down here.”

Mr Floyd’s older brother, Terry, was last seen walking along the Pyrenees Highway between Avoca and Maryborough on June 28, 1975.  

The 12-year-old had spent the afternoon playing monopoly at a friend’s house and was expected to be home for dinner, but he was never seen again.

Mr Floyd was 10 at the time of his brother’s disappearance. It’s a heartbreaking reality that has taken a heavy toll over the years.

“Every year I think that we should be off fishing,” Mr Floyd says.

“We did it as kids. But that was taken away.”

Mr Floyd is certain his brother was abducted and murdered that winter’s afternoon, before being dumped in a nearby mineshaft.

Former Homicide Detective Ron Iddles - who worked the cold case from 1999 - also believes that Terry Floyd met a fateful end wandering the highway between Avoca and Maryborough.

“In my mind there’s no doubt he’s been murdered,” Mr Iddles says.

Mr Iddles says the prime suspect in the 43-year-long mystery is convicted pedophile Raymond Jones.

At the time of Terry’s disappearance witnesses told detectives they saw him standing next to a light-coloured Holden panel van that had pulled up beside him.

Their description matched the vehicle driven by Jones at the time.

“He is a suspect and remains a suspect,” Mr Iddles told Steinfort.

“But if you don’t have the crime scene and you don’t have the body, it’s difficult.”

While his brother’s body remains missing, Mr Floyd’s physically - and emotionally - taxing quest continues.

“My brother does not deserve to be laying in that disgusting mine out there,” Mr Floyd says.

“If the situation was reversed my brother would do it for me”

This Sunday, Steinfort joins Mr Floyd on his determined mission as they both confront the convicted pedophile at the centre of the case for the very first time, in a desperate bid for answers.

And – in a shocking twist – one of Jones’ alleged victims reveals a harrowing testimony which is sure to blow the case wide open.

© Nine Digital Pty Ltd 2018