Detectives reviewing the 1978 killings – which bear an eerie similarity to the cult film Wolf Creek – say the case is “definitely solvable”.

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It is examined in a four-part podcast series, produced by The Courier-Mail, called Spear Creek.

Karen Edwards, 23, her boyfriend, Tim Thomson, 31, and his friend, Gordon Twaddle, 21, were days into a trip around Australia when they were lured into the bush and gunned down.

The friends left Alice Springs on October 2, 1978, on two motorbikes – Tim carrying his Doberman puppy, Tristie, on a homemade sidecar. But police believe that somewhere between there and Mount Isa they were befriended by another “motor­cycle enthusiast”.

He camped with them at Barry Caves and accompanied them into Mount Isa, where the three friends booked in to the Moondarra Caravan Park for two nights.

“It is believed that on the evening of Wednesday, October 4, 1978, a fourth person attended in a Toyota Land­Cruiser, with the group socialising at the campsite,” homicide detective Senior Sergeant Tara Kentwell said.

The person went home but returned in the morning to collect the group in his 4WD. He returned on nightfall – alone – to dismantle the campsite. He was also heard calling to Tristie.

Police believe that by October 6, everything but Tim’s homemade sidecar had been removed from the caravan park.

Gordon’s bike, a 1977 Suzuki GS750, was found abandoned at Mount Isa’s Golden Fleece Service Station. It was believed to have been left there on October 5 – the day the three friends were last seen alive.

But police believe Tim’s 1977 BMW R100S was taken to the Kmart shopping centre then moved again on October 6.

“Police believe Tim’s motorbike, the red BMW, was being ridden in and around Mount Isa between October 6, 1978, and November 13, 1978,” Sen-Sgt Kentwell said.

“We are seeking anyone who may have seen either the blue Suzuki motorcycle or the red BMW motorcycle being moved from the Moondarra Caravan Park into the Mount Isa CBD on or around October 5, and subsequently ridden around town, to please contact police.”

Mount Isa man Bruce John Preston, then 22, was found with the bike after a neighbour contacted police. He was charged with theft and fined $300. Nobody has been charged in relation to the murders.

Anyone with information should call Crime Stoppers on 1800 333 000.