A family turf war, double murder, and an affair: the cold case that haunts Far North Queensland.

For 20 years now, a suspicious disappearance in the Top End's Cape York region has left the community shaken.

In 2003, fisherman Bevin Simmonds, 36, and his son Brad, 10, vanished while checking their shark nets. No trace of them was ever found - no bodies, no boat, no murder weapons, and no witnesses.

But police believe there's a murky truth beneath it all. And the isolated community up in the Far North Queensland region has been forever changed by the tragedy. 

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Near the Coleman River in the Cape York area, lived two rival fishing families.

For generations the two families - the Wards (which Bevin and Brad were a part of) and the Gaters - have been the main fishing families in the area. They made a living on whatever they could pull from the sea, most commonly barramundi. 

As one local noted recently about the region: "If you haven't got a criminal record, you don't live in the gulf. That's what a lot of people there say. They're fighting sharks, fighting crocodiles, fighting each other. If there wasn't three fights in the pub a night, the pub was closed. It's like the wild, wild west really."

Justine A Rosenthal is an Emmy-award-winning filmmaker, who recently co-directed the new Stan Original Documentary Revealed: The Cape.

Speaking with Mamamia's True Crime Conversations, she noted just how isolated the area is - and why that perhaps worked to the advantage in the presumed-murder case of Bevin and Brad. 

"The scenery is lawless. Everyone there has guns and you are out there on your own, hoping for the best. The Indigenous community on the other hand though, has a very different relationship to the land than the fishing communities, who are more at war."

Bevin Simmonds wasn't originally from the Cape York region. He'd grown up in regional cattle areas, Rosenthal saying Bevin never truly "felt a part of that world [Cape York] even though he lived in it".

Bevin Simmonds and Cathy Ward met at school. She became pregnant with their child, and she reportedly wished to return to her family's fishing roots in upper North Queensland, so the couple moved there.

Cathy was from one of the biggest fishing dynasties - the Wards. 

"I would say the Wards are slightly more the upstanding citizens of the community, compared to the Gaters. Those two families were originally very close - the children played together growing up. The Gaters have many children, and one of them was Michael Gater, who is about the same age as Cathy Ward," Rosenthal tells Mamamia.

The area in question. Image: Stan.

According to friends of Bevin's, they say he was more of an outsider in the community, nor was he fully accepted by the two fishing clans.

By June 5, 2003, Bevin and Cathy had three children together - Katie, Brad, and another child.

That day Bevin and Brad set out to check their family's shark nets 5km from the mouth of the Coleman River. Usually, Katie would accompany her father on shark net checks like these, but she reportedly had something on, so 10-year-old Brad went in replacement.

There remains confusion over whether anyone knew Brad would be going out to check the shark nets with his dad that day. Mainly, there's confusion over whether he was an intended target, or found himself at the wrong place at the wrong time.

Bevin and Brad took off in a substantially sized dingy, fit with life jackets, fishing equipment and more. There is evidence that the pair made it to the shark nets to go about their task of clearing them. 

But the job was only half done - leading detectives to strongly believe an event occurred midway through the pair clearing the nets. They believe that event was a double murder. 

When Bevin and Brad went missing, Bevin's wife and Brad's mother Cathy started the search, along with a member of the rival fishing family, Michael Gater. Four days into the disappearance, police came up to the region. What followed was a large air, land and sea search to try to find the pair. 

In the days and weeks that followed though, no evidence was recovered - no bodies, no boat, no murder weapons, and no witnesses. To this day, the final resting place of Bevin and Brad is unknown.

Given the size of the duo's dingy and all that was in it, police said it was surprising and suspicious that they were unable to recover any evidence from the boat. If the boat had capsized in any way, it would be assumed some sort of paraphernalia would float to the top. 

There wasn't any evidence of the boat's motor, oil or fuel either. And that's highly unusual. 

Bevin and Brad Simmonds. Image: Stan/QLD Police.

While investigating Bevin and Brad's disappearance, police grew suspicious.

"They hear whispers of an affair between Michael Gater and Cathy. She denies it to police for quite some time. And the denial itself is suspicious - why would you pretend something isn't happening when everyone in the community knows something is going on," Rosenthal tells True Crime Conversations. 

Soon after this point was made to police, their attention turned to Michael Gater and his mother Joan Gater. 

During the investigation, the community confirmed the rumours of a brewing turf war between the Wards and the Gaters. Many people in the fishing community said they believe this family rivalry turned deadly.

Police then started to believe Joan Gater "isn't keeping her story straight".

"They've got all kinds of rumours. Guns go missing, Joan and Michael Gater were on a boat nearby at the time of the disappearance," says Rosenthal. "A friend of Bevin's then recounts in the documentary that he had a conversation with Joan. He says that Joan said one of her relatives in Papua New Guinea had learned how to get rid of bodies in ways they would never be found."

It was soon confirmed that Michael and Cathy were having a sexual affair. 

In 2005, Joan and Michael were charged and acquitted of the alleged double murders in a Cairns Supreme Court trial.

No other leads or suspects have ever been found.

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From Rosenthal's perspective, she says lots of people were "scared to talk".

"In the end it was a solely circumstantial case with no evidence and no witnesses. People go missing in the Cape. The Gaters have a reputation for that [being dangerous], they've been charged multiple times. There is no law and order. Even the MP there, Bob Katter, says that."

As Rosenthal notes: "When you are pushed to the extremes of your humanity, what are you capable of?"

So far, the biggest theory as to why Bevin and Brad were killed is the relation of the love triangle between Cathy and Michael. According to Rosenthal, the relationship did not continue.

"Bevin and Michael had had a physical dispute in the days leading up to Bevin and Brad's disappearance. Certainly according to Bevin's family, he was well aware of the affair, as was everyone else. One wonders if the 10-year-old boy had not been there [when the potential murders occurred], what would have happened? I'm not even sure there would have been an investigation if just Bevin had died, as going missing is so normal up there."

In the decades since, the mystery of what happened to Bevin and Brad has continued to haunt Far North Queensland. 

Image: Stan. 

"People wonder if they had said something, spoken up earlier, could this have been avoided. I think there is a sense among everyone that the little boy was never intended to be a victim. And that may be where the real sense of guilt lies with everyone," Rosenthal says.

Katie Simmonds, who was 12 when her father and brother disappeared without a trace, has the words 'Brad' and 'Justice' tattooed on her skin. 

"I just want to know what happened," she told Daily Mail recently. "I just want to know where they are, where the boat was sunk, just give me the GPS co-ordinates. All I've got is a million miles of water to look at and no answers."

Stan's Original Documentary Revealed: The Cape is based on nearly two decades of research, access, footage, interviews, and a podcast investigating the unsolved cold case.

Amid new podcast deep dives into the case, this documentary and more, police hope new interest will result in answers. 

Ultimately, the quest for justice continues for the families of the victims, who hope to one day find out the full truth of what happened to Bevin and Brad Simmonds.

Feature Image: Stan/QLD Police.