David Sneddon disappeared in 2004 and is believed to have been abducted by North Korea.
In August 2004, a 24-year-old student from Utah was hiking through the lush Tiger Leaping Gorge in China's Yunnan Province when he disappeared.
He'd cheerfully parted ways from his college roommate George Bailey and was due to meet brother Michael in Seoul after, to head home to the US. He never made it to South Korea.
The Chinese authorities told his family they had figured out what happened - David Sneddon had fallen to his death and drowned.
But when his father Roy and brothers James and Michael retraced his steps to find evidence of his demise, there was nothing. No passport, no bag, no clothing, no body. What's more, the trail was an easy one and David was an experienced hiker. There seemed no way he could have had a fatal accident there.
Even more strangely, they met a series of people who remembered the friendly young American, and had seen him after he had walked the gorge.
A Tibetan hiker said he had travelled with David to the other side. Other witnesses said they had seen him at a Korean restaurant in the nearby tourist city of Shangri-La on August 14.
Later, the same people told police they could not be sure.
"We were, I suppose, naive," Roy told news.com.au. "We had all these sightings we felt good about and went to Shangri-La ... we said, hey, we have all this information they haven't shared with the police.
"It became evident they weren't going to do anything. The Korean cafe was about 100 metres from a police station, all they had to do was walk down the street, and they didn't do it for six months. The Chinese police are not incompetent."
David mother Kathleen goes further. She says those witnesses were "terrified" about what might happen to them if they spoke further.
And that might have been the end of the road in David's case. But seven years later, Kathleen received a remarkable call from a senior Pentagon official, suggesting her son had been kidnapped by the North Korean regime as an English tutor for Kim Jong-un.
The idea sounds implausible, but that's North Korea. On the other end of the line was Chuck Downs, deputy director at the Pentagon's East Asia office and a human rights committee director. He laid it out for the shellshocked Sneddon family.
North Korea has been kidnapping foreigners for more than half a century to assist in training intelligence officers - thousands from South Korea, along with several hundred from Japan and China and a handful from other nations around Europe, Asia and the Middle East.
Yunnan province is known as an "underground railroad" for North Korean refugees, a network of safe houses and routes through which defectors are smuggled from China into Southeast Asia, aided by Christian activists from the West.
Downs suspected David could have been mistaken for one of these smugglers by agents operating on the routes, but as time passed and the Sneddons dug into the possibility further, a more sinister theory emerged.
David's exceptional language skills from teaching in South Korea would have made him a valuable individual for Kim Jong-il, who had been kidnapping foreign linguists to train his spies since the 1970s.
The law and languages student spoke both Mandarin and Korean, and his disappearance came just months before regime was due to release US Army Sergeant Charles Jenkins, after 40 years in captivity serving as an English teacher.
Jenkins, who was interrogated for 10 days before he was transferred to a fortress-like house with two other Americans where he was captive for decades, later wrote: "I suffered from enough cold, hunger, beatings, and mental torture to frequently make me wish I was dead."
The head of an NGO told the Sneddons they suspected the regime may have taken David as a replacement for Jenkins, to teach English to the regime's senior diplomats, spies, or even future leader Kim Jong-un.
David's sudden disappearance has unsettling parallels with the frequent abductions of Japanese people by the North Korean regime, in which agents snatched victims from inside Japan.
Many of those abductees went missing shortly before North Korea's Liberation Day, August 15. And they often vanished from Korean restaurants or cafes.
The North Korean regime frequently arranges marriages for abductees to stop them trying to escape. Last September, the Sneddons heard from South Korea abductees' advocate Choi Sung-yong, who said an informant had spotted an American fitting David's description living in Pyongyang.
He goes by the Korean name Yoon Bong Soo and is married to a woman named Kim Eun Hae. They have two children, a boy and a girl.
When news.com.au spoke to Roy and Kathleen, both 81, over the phone from their home in Logan, Utah, these Mormon parents to 11 children sound weary but indefatigable.
"It's just been a difficult last couple of days," says Kathleen, who has been inundated with calls after American Otto Warmbier's tragic return from detention in North Korea.
The 22-year-old's family were told he had been in a coma for more than a year after contracting botulism and taking a sleeping pill. He died in an Ohio hospital on Monday.
"It is our sad duty to report that our son, Otto Warmbier, has completed his journey home," his parents Fred and Cindy said in a statement.
"The awful torturous mistreatment our son received at the hands of the North Koreans ensured that no other outcome was possible."
David's parents can only hope their son, who would now be 37, will be luckier. "Ever since we've known about Otto my heart's gone out to the family," says Kathleen.
"I think sometimes mothers have different feelings than other people do, very tender hearted."
Roy believes Otto's father is maintaining a "strategic silence", and is "working quietly behind the scenes."
David is not on the list of American detainees who US secretary of state Rex Tillerson is demanding North Korea release, but Senator Mike Lee and Congressman Chris Stewart have been campaigning for their cause for years.
The family believe anger over Otto's case may offer an opportunity for them, which they are determined to grab with both hands.
"You're watching the next step," says Roy. "We're right in it, right now. How it turns out, I do not know."
It's been 13 years since David dropped off the face of the earth, but the Sneddons have never lost their faith.
They have meticulously collected evidence, setting up a website helpfinddavid.com, which includes their "executive report", photos and information collected over years of research that has taken them from China to Tokyo to Washington.
They have met with a multitude of NGOs, human rights advocates, Japanese government officials - who are convinced David is a victim of kidnapping by the hermit state.
"Our latest information on David's case points to David's likely abduction by elements of the Democratic People's Republic of Korea (North Korea)," says a post from August last year. "We believe he is now being held captive there."
The Sneddons are bruised by the lack of interest from the US Department of State, which maintains there is not "credible evidence" David was abducted. They presume their story "doesn't fit the narrative" the department wants for US-China relations.
"The 'credible evidence' David was drowned in the gorge was the Chinese said that's what happened," says Roy.
"They've never really investigated a lot of material," adds Kathleen. "They may have been investigating it privately. That's my hope, that they're silently working on it."
Her husband is less patient. "If you're suddenly thrown off a ship and pray a dolphin will come and give you a ride, you're probably best off to start swimming yourself," says Roy.
"We decided we'd try swimming ourselves. There's so much politics, it's difficult."
Kathleen trusts her son is probably safe for now, but her eyes are wide open to the dangers and she sees clear reasons why their son might not have been able to contact them for all these years.
"If [Kim Jong-un] didn't like David anymore, he'd be killed," she says. "The internet is absolutely closed in North Korea. Some people may have access to a phone from China, but he probably doesn't want to jeopardise himself and his wife and children.
"If any one of our children had to be abducted and cope with a difficult situation, it's David. He has great personal belief, on the inside he's very strong.
"I just want to run up to him, hug him and get to know his wife and children."
Despite their desperation to see their son again, the Sneddons have also found room in their hearts to feel deeply for the North Korean people. "It's such an evil and repressive empire," says Kathleen. "I hope David is freed and something happens and these people will be freed."
As they watch the pressure on North Korea increase over its repressive regime and nuclear testing, they wonder if their "adjustable" son could even play a vital role in a transition.
"I'd like to think, in the long run, David could be a blessing to the people of North Korea," says Kathleen. "I hope David can move mountains." She laughs. "We're both dreamers."
Roy interjects: "I don't think we are. I believe Kim Jong-un's regime will fall. It won't happen because the US sends an aircraft carrier, it'll be because people watching in positions of power say, enough is enough."
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