Pictured: Penny Farmer, now 57, of Manchester
For the best part of four decades, a nagging sense of injustice gnawed away at Penny Farmer – someone had brutally murdered her older brother and his girlfriend, and the killer had got away with it.
Penny, now 57, decided to continue the detective work her father had started and tried to find their murderer – by using Facebook.
Penny was just a teenager growing up in Chorlton, south Manchester, when her brother Christopher Farmer, a newly-qualified doctor, set off on a round-the world trip with his sweetheart Peta Frampton, a lawyer.
They left the city in December, 1977, but never came back.
The couple were brutally murdered in central America, seven months into what should have been a trip of a lifetime.
Writing home regularly as they travelled around the world, the pair revealed they had met a charming American called ‘Dwayne’, who had offered to take them from Belize to Mexico as crew members on his 32ft wooden sailing boat, the Justin B.
In Peta’s final letter, postmarked June 29, 1978, she wrote: ‘Enough of the future. I don’t think there’s any more news – nothing much happens on a boat. Lots of love Peta.’
The lack of letters from this point forward was a clear sign to their families that something terrible had happened.
Christopher’s father Charles Farmer, a BBC journalist, made his own enquiries to find out where the pair were.
He appealed for help in the Belize Times to no avail. Following this, he hired a local man, Alphonso de Pena, to act as a private investigator.
By January 1979, Mr de Pena learned through a local priest living just over the border in Guatemala that the unidentified bodies of a young European couple had been pulled from the water 200 metres from the shore the previous year.
The two had been tortured, beaten, bound and thrown into the sea, weighted down by heavy machine parts tied to them.

Peta Frampton and Christopher Farmer the day before they set off in December 1977
This terrible crime had happened in the first week of July, 1978 – days after Peta’s last letter.
Soon after, local fishermen had discovered the bloated corpses of the two, then-unidentified westerners, who were buried in unmarked graves.
After the private investigator’s breakthrough, the bodies were exhumed and dental records were flown across the Atlantic to confirm it was Christopher, 25, and Peta, 24.
It was devastating news for the families back home in Chorlton.
Charles and diplomats at the Foreign Office continued to make enquiries, tracking down the owner and skipper of the Justin B.
That skipper was an American called Silas Duane Boston, a shady drunk who – it would later emerge – was on the run in central America, wanted on a charge of statutory rape against a minor back home in Sacramento, California.
The British consulate and Charles both managed to speak to Boston by phone.
He was evasive and unconvincing, telling the consulate his two passengers had disembarked because his boat had required repairs.
To Charles, he said: ‘Let me know if you hear anything about them’, claiming he didn’t know what had happened to the couple.
After that, Boston seemed to disappear off the face of the earth. Charles Farmer died in 2013, at the age of 91, without ever getting to the truth.
That nagging doubt, that sense of injustice, lived on in his daughter Penny, who decades later finished what her father had begun.
Her ‘lightbulb moment’ came while she was out on an autumn walk with her mother Audrey in October 2015, when they reminisced about Christopher.
‘I wonder what Chris would have looked like. He’d have been 62 now. He’s forever young in our eyes, isn’t he?’ said Audrey wistfully.
It dawned on Penny that she should turn detective, using the internet as her main tool.
Her heart racing, as soon as she got to a computer screen she did a Facebook search for Boston’s two sons, Vince and Russell.
These names had been on the manifest of the Justin B and had also been mentioned in the letters sent home by the couple.
The skipper had brought his young lads, then 13 and 12, with him. Surely, they would know something?
Penny quickly found Boston, then 74, online – his grizzled Facebook profile picture staring at her through the screen, and his two sons.
She was relieved. At least he was alive. She was also furious. Why had she not done this years before?
Penny messaged the sons and, at long last, discovered the truth.
They told her they had seen their father kill. The two men said they had witnessed their father tie up the couple and toss them into the sea, apparently furious that Christopher had chided him for bullying his younger son aboard.
Drunken Boston had taken a swing at Christopher but ended up falling overboard, before muttering darkly about taking revenge.

Duane Boston (pictured) was charged with murdering Christopher and Peta
According to Vince, his father told Christopher to pull up the anchor, crept up behind him and repeatedly bludgeoned him over the head.
He then attempted to stab Chris in the chest with a fillet knife but the blade broke and Chris cried out: ‘I give up!’
The following morning, Boston is said to have told the couple he was going to drop them near Livingston, Guatemala, tying their hands and stripping them naked to stop them reporting him to the police before he could escape.
Over the next 36 hours, Boston allegedly taunted and bound them and put plastic bags over their heads, tying them to blocks of metal and then throwing them overboard, fully conscious.
The horrific details of the case – and the fact it had taken so long to get to them – shook Penny to her core.
She went to Martin Bottomley, the vastly experienced, grey-haired head of the cold case unit at Greater Manchester Police, and begged him to re-open the case.
Her mother Audrey wasn’t getting any younger and she was desperate to see justice done.
GMP contacted Interpol and Sacramento Police, who quite by chance had re-opened an investigation into the disappearance of Vince and Russell’s mother Mary Lou in 1968.
Her disappearance was one of a dozens of apparent murders and rapes which police in California had re-examined.
Today Sacramento Police is said to have two large files totalling 2,000 pages which implicate Boston in crimes going back 50 years, including the death of Mary Lou and other murders.
Within two weeks of Penny making contact, Vince Boston gave Sacramento Police a statement, testifying that it was an open secret that his father had killed his mother and that he had witnessed him murdering Peta and Christopher.
Russell would give a similar testimony.
Both Vince and Russell would go on to claim that they had tried to alert the authorities on both sides of the Atlantic over the years but were told no file could be found in England recording Chris and Peta’s murders. Alerted by Penny, GMP looked for but could find no trace of its file on the case.
Then a breakthrough: they contacted a long retired detective who had been involved in the case, David Sacks, to ask him what he could recall.
Yes, he did remember the case and, amazingly, he had kept a full copy of the file in his garden shed.
Some 38 years after their killings, Sacramento Police finally tracked down Boston in December, 2016, and he was charged with the murders of Christopher and Peta.
Penny and her family pleaded with the court to hasten proceedings, as Audrey wanted to see justice done before she died.
The family was even willing to forego an entitlement to seek the death penalty upon conviction in an effort to speed matters up.
But still Boston managed to conclude matters on his own terms. With deteriorating health because of years of alcohol abuse and with just three weeks before Penny and Audrew were due to attend a pre-trial hearing, Boston died in jail, aged 76.
He had been on dialysis but he is said to have ordered medics to withdraw treatment.
Within hours, Penny and Audrey, who had been preparing to travel to the US, were told the news. There would be no day in court for them. They would not have the satisfaction of looking him in the eye in the dock.
Penny, who now lives with her mother Audrey, 93, in Oxfordshire, said: ‘I was gutted, absolutely gutted. I thought we were going to see justice.
‘I was ready to stand up in court and tell them what a monster he was. But he wouldn’t even let us have that. It took quite a while to get over that. The game was up for him.
‘I wouldn’t like to say suicide but he did it for a reason and that was because he knew the game was up. It was really gutting.’
Vince said: ‘My mother was also a victim of his. He killed my mother when I was four years old. Of course I have sympathy for those families he’s hurt and all the pain he’s caused over the years.
‘I’m in anguish for what he did to my mom. She was only 23 years old. He murdered her. My father caused a lot of pain and suffering for a lot of people and pretty much got away with it all. It’s at least some kind of justice he’s not among us anymore. But unfortunately this case wasn’t able to go to trial. He’s gone and he can’t hurt anybody else.’
Court documents outlined a truly shocking case against Boston even though the proceedings never reached the denouement the families craved.
Vince Boston testified that his father repeatedly struck Christopher Farmer to the back of the head with a wooden ‘billy club’ as the young doctor is said to have cried: ‘What’s your game? What’s your game?’
When his girlfriend emerged from the galley, Boston is said to have threatened to shoot her with a spear gun.
The skipper then ‘hog tied’ his passengers at the rear of the boat and put plastic bags over their heads before pushing first Christopher and then Peta overboard, followed closely by the machine parts to which they were attached by a length of rope.
‘Boston looked at his watch and after three or four minutes stated ‘OK they are dead now’,’ the dramatic testimony revealed.
Despite finally getting to the truth, Penny despairs that Boston has escaped justice.
‘I’m sorry but four months in prison does not equate to justice in my book’, she said.
Now, she has written a book Dead In The Water about the crime and her efforts to get to that truth, which had remained secret for almost 40 years.
Penny explained: ‘First of all I wanted it to be a lasting memorial to Chris and Peta who were two great people. They were so loved. There’s not a day goes by we don’t think about them. Secondly, you can’t deny it’s a truly remarkable story.
‘It’s the most incredible story which I wanted to be told accurately and truthfully and my family and I are part of that story. Why wouldn’t I write it? It’s my family’s story to tell.’