Twenty years ago, Alex Ratnasothy told his family he was going on his "greatest adventure yet" in Nepal. They never heard from him again.
The 23-year-old, from Grays, in Essex, was due to come home in April 2003.
On 21 February 2003, he warned via email he would not be in contact while he made a nearly month-long trek towards Everest basecamp.
His last words to his family were: "I'll be back before you know it."
But he never did return.
In July 2003, the month of Alex's 24th birthday, his sister Dr Anna Crozier and his elder brother Dr Joel Ratnasothy took time off work and travelled to Nepal. They discovered he had been robbed of all his possessions, even his shoes, and then seemingly disappeared.
Two decades on, Dr Crozier says her father's health is deteriorating and it "suddenly feels urgent" to get answers.
If you had asked about her brother's disappearance a week ago, Dr Crozier would have said that she assumed he was dead.
However, as the 20th anniversary of his disappearance approached, she found herself going back over notes from the 10 months she spent in Nepal searching for him.
She now wonders if he may have chosen not to be found.
"I thought he can't be alive or he would have contacted us - but now I think back and think he was scared after the robbery," says the doctor, from Chelmsford.
One person told them they saw a man they believed was Alex barricade himself into a room at a hostel, showing he was "clearly distressed", she says.
Alex would now be turning 44. Over the years, he has never been far from the minds of family and friends on anniversaries, birthdays and other family occasions.
"It feels like a branch of our tree is missing," says Dr Crozier.
"We all met on what was his 40th birthday and it was really painful. That was awful, because he wasn't there."
In an age before social media appeals, Dr Crozier, now 47, and her brother Dr Joel Ratnasothy, now 46, retraced their brother's steps with the help of a local guide in 2003.
Over the course of a few weeks, they learned he had been robbed of his money and possessions but had left his passport at a travel kiosk after trying to arrange a flight to Dubai.
"Every day I think about himâ¦ It's literally been since last week and I remembered he came back to Kathmandu and asked for a flight to Dubai. If he survived the robbery, what's he doing, where is he?"
Dr Crozier believes her brother was targeted by robbers because "he was vulnerable" as he was "on his own". She thinks it may have "triggered a breakdown".
His trip to Nepal was was part of a year of travelling for the computer science graduate.
Dr Crozier spent 10 months searching for any clue about her brother. She talked to locals, established he had travelled to the Arun Valley in Nepal then returned to Kathmandu in early April 2003.
He had looked to book a flight to Dubai but after that the trail went cold.
Flying home "realising we hadn't found him" was "really awful" , she says.
With their father Anthony's health deteriorating - and exactly 20 years since his last contact with them - Dr Crozier says it seems "suddenly urgent" to find answers.
"It would be tragic and heart-breaking if Dad died not knowing," she says.
"I hope he's got a life. He doesn't even need to contact us directly, just let us know if he's alive, particularly for Dad."
As a mother herself, Dr Crozier says the experience of her brother being a missing person has put things into perspective
"It really does make you realise and appreciate what's important in life. All that matters is my children are safe; everything else is minor details.
"It's been hard on all the family."
Dr Crozier is keen to hear from anyone who may have seen her brother or who may have information about his disappearance.
She says people may remember him from identifying details such as a large Chinese dragon tattoo on his back.
"I do have some hope," she says. "You do hear stories sometimes of people being found."
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