That is the question nagging the family and friends of Danny Hall, a British backpacker who went missing in the southern Thai resort of Koh Pha Ngan six months ago.
The disappearance of the 36-year-old - last seen on 25 February - has baffled investigators and loved ones alike.
A roadie and former winner of TV quiz show The Weakest Link, Mr Hall had been on his third trip to Thailand when he was last seen after the island's world-famous Full Moon Party.
Every month, it is estimated up to 25,000 revellers descend on Koh Pha Ngan for the all-night beach rave.
For most of the party-goers their worst experience is likely to be waking up with a hangover.
But the British foreign office website warns that incidents of date rape have been reported at the event.
The Bangkok Post reported in April that a Koh Pha Ngan police chief had recently been transferred amid a rising crime rate and complaints about visitors' safety.
Meanwhile, a number of accounts of tourists being attacked on the island can be found on internet travel chatrooms.
Mr Hall's friend, Roy Twemlow, was one of the last people to speak to him when he rang Mr Twemlow from a bar, in the afternoon following the Full Moon Party.
The pair became friends at Birmingham University, where Mr Hall, from Norwich, England, graduated with an honours degree in history.
The 36-year-old said: "It was about 2pm when [Danny] rang me and he sounded fine, he didn't sound panicked. It's just not like him to vanish without trace.
"I've kind of accepted I'm never going to see him again. But someone must have seen something, someone must know something.
"Danny's very sociable, makes friends easily and is highly intelligent. He's also very non-confrontational."
On arriving in Thailand at the end of January, Mr Hall, who had worked as a roadie for The Rolling Stones and at England's Glastonbury music festival, spent a week in Bangkok at Mr Twemlow's home.
"He wasn't moping around or depressed," recalls his friend. "It was just the same old Danny."
Mr Twemlow, a teacher who has lived in Thailand for a decade, travelled down to Koh Pha Ngan to investigate after Mr Hall had been reported missing.
He expected to find police on the island in the midst of a full investigation when he arrived at the end of April.
But he says: "When I got to Koh Pha Ngan, the police knew very little about the case, they hadn't even searched the area where Danny was last seen. It's a bit of a disgrace really."
Mr Twemlow found his friend's possessions - a backpack and an acoustic Yamaha guitar - left in his accommodation, a hut at the island's secluded Hat Yao beach. But Mr Hall's passport and money belt have not been found.
American backpacker Chris Chester, who met Mr Hall on Koh Pha Ngan a week before his disappearance, but did not attend the Full Moon Party, raised the alarm within three of four days of the Briton vanishing.
The 39-year-old said he and his German girlfriend had met up with Mr Hall almost daily, going to the beach, relaxing with a massage and shopping.
"He had been in regular contact with us the whole time, so when we didn't hear from him for a couple of days I thought it was pretty strange. I started trying to find him and asking around," he said.
Mr Chester checked hospitals and clinics on Koh Pha Ngan and neighbouring Koh Samui in his search for the missing tourist, but to no avail.
"There was nothing to suggest he was depressed. I really can't fathom what happened to him," he said.
Mr Hall is known to have joined dozens of party-goers at the Backyard Bar for an "after-party", on the morning after the Full Moon rave.
Niki Kursakul, 45, from Sydney, Australia, who is married to the Thai owner of the bar, described Mr Hall's disappearance as "totally bizarre".
The mother-of-two, who has lived in Thailand for 16 years, said: "It's very, very strange. The bar isn't near a beach but I suppose it's possible he could have wandered down to the sea, gone swimming and got into difficulty.
"But a body would usually get washed up if someone drowned. If he'd fallen or had an accident near the bar he would have been found by now.
"There can be the occasional fight [in the Backyard Bar] but no-one saw any argument taking place that day as far as I know."
Bangkok's ministry of foreign affairs said the Thai authorities were working closely with Mr Hall's family and friends and the British embassy to investigate his disappearance.
Spokesman Tharit Charungvat said: "The safety of tourists in Thailand is a matter of great concern to the Royal Thai Government."
He said the number of visitors to Thailand was on the rise and that the country's popularity was "due, among other things, to the hospitality and safety tourists can expect when visiting Thailand".
Thai Police Colonel Chataree Pandum said Mr Hall's bank account remains dormant since he disappeared and investigators believe the Briton did not leave the island.
Norfolk Constabulary in England said they were treating Mr Hall as a missing person - as is the UK foreign office - but that officers currently had no plans to travel to Thailand.
In the meantime, the agony for Mr Hall's loved ones continues.
6 months ago