IN July 1978, two tortured bodies were found floating off the coast of Guatemala in central America, the remains of junior doctor Chris Farmer and his lawyer girlfriend Peta Frampton.

Beaten, and weighted down with heavy engine parts and plastic bags over their heads but still alive, they had been thrown overboard from the yacht on which they had been crewing.

For nearly 40 years no one was charged with the brutal murders but efforts made by Mr Farmer’s sister Penny, and her family, helped bring the killer to justice.

The journalist and mother-of-three, who worked for the Oxford Mail in the 1990s, used social media to track down the boat’s owner, Silas Duane Boston, who had spent his life on the run.

The story of the tragedy, and how the killer was brought to justice, has now been told in Ms Farmer’s book, Dead in the Water, published by John Blake.

In the book’s preface Ms Farmer, 57, who lives in West Oxfordshire, said: “This a true account of the tragedy that befell my family in July 1978 and its denouement, nearly four decades later.

“The turn of events, both then and now, has at times stretched credulity, but, as they say, life is stranger than fiction and the best stories are always true.

“I can say with full conviction: final closure only comes when the truth is known.”

The disturbing account includes eyewitness accounts of the killer’s two sons, Russell and Vince, who aged 12 and 13 respectively, witnessed Chris and Peta’s ordeal and gruesome murders.

Thanks to the work of Greater Manchester Police, the FBI and the Sacramento police department, 76-year old Boston was arrested in Sacramento in 2016 and the full extent of his hideous life of murderous crime was, for the first time, laid bare. He died in April last year awaiting trial.

In the book’s epilogue Ms Farmer’s mother Audrey writes: “As long as I live I will never forget the sense of utter desolation on hearing news from the Foreign Office, in February 1979, that two bodies had been found floating in the sea off the Guatemalan coast and we were to prepare ourselves for them being our missing two but literally nothing can prepare you for that.”

She added: “There is not a single day that I haven’t thought of him (Chris) and in so many ways it is an unending tragedy but time has blunted the initial heart-stopping shock.”

Detective Amy Crosby, of the Sacramento police department, said the murder case was the most complex of her career.

She added: “Silas Duane Boston was a fascinating, yet horrifying person, who led a life of death, destruction and doom. The collaboration between prosecutors and investigators that spread across three continents was incredible.”

Dead in the Water is published by John Blake, price £8.99.