© Doug NashMysterious death ... Doug Nash with Silvia Fink, who died after a five-year romance aboard the yacht Windcastle, now riding out the cyclone season.
In the harbour of Port Vila, a husband awaits scientific explanation of his wife's agonising end.

Doug Nash and Silvia Fink met and fell in love on a yacht. After their 2007 marriage, the Windcastle took them to the still-warm lava of the Galapagos Islands, to Tonga, where they met the Pacific's last king, and on to New Zealand, surviving a ''pasting'' on the famously rough crossing.

''She was just crew but she ended up staying five years,'' Nash says. ''We had a tremendously successful romance and developed a great partnership. Our goal was a complete circumnavigation, but that came to a screeching halt in August.''

Their boat now floats on a mooring in Port Vila harbour, Vanuatu, riding out the cyclone season. By the time it sets sail again, at least nine months will have passed since it was the scene of 56-year-old Silvia's sudden and mysterious death. In the meantime, her widower waits, and waits.

Nash's nightmare began after sailing from Vila to the island of Epi, 145 kilometres north, on an August day after the island's annual canoe-race festival. Lamen Bay was lively when they dropped anchor and Silvia spent an evening playing with village children, teaching them how to dance.

The following day, anchored in the bay, she took MMS - Miracle Mineral Solution, a compound she had bought from fellow sailors, a Belgian and a Californian, who had assured her it would ward off malaria in the Solomon Islands, Nash and Fink's next destination.

Nash, 77, is a retired NASA geologist, a man of science, sceptical about the claims on the bottle. But he stayed out of it, he says, because she was ''a grown and savvy woman''.

''It went bad from the beginning,'' he wrote to friends in the days afterwards. ''From almost the moment she drank the mixture of MMS with lime juice that she'd brewed up according to the instructions ... she began to be nauseated, and soon was vomiting and on the toilet having diarrhoea.

''But she thought, because the literature that came with the MMS kit emphasised that these were normal symptoms, that one just had to grin and bear it when first using the substance. How wrong we were. It turned into torture the whole day, with her getting gradually worse and worse, having incredible abdominal pains, then urinary pains.

''I'd been helping her all day, bathing her, emptying the bucket, comforting her, trying to get liquids down her, all to no avail because she could not keep anything down. Eventually, about the time it was getting dark, she started having feelings that she was going to faint. That's when I became fully alarmed. I got on the VHF radio and called for assistance.

''At that moment she suddenly went into a coma. Then I put out another radio call, this time an emergency one for immediate medical help. Fellow cruisers rushed to our boat within minutes to aid me, and for over an hour we conducted emergency CPR and administered oxygen but it, and an adrenaline shot administered by a physician who finally arrived from the village, failed to revive her.

''And she died on Windcastle around 9pm, just 12 hours after she'd taken that fatal drink of MMS.''

Both married before, Nash and Fink met after he advertised for crew in San Diego in 2004. ''I miss her immensely. Windcastle is empty without her presence.''

Vanuatu, a volcanic archipelago supporting 240,000 inhabitants on a latitude with Cape York, looks like paradise to outsiders who dive and sail its turquoise waters. But the death of this vivacious Mexican exposed the full catastrophe of petty island bureaucracy and under-resourcing that bedevils the place.

The 80-odd islands James Cook named the New Hebrides in 1774 have become a purgatory for Nash in the months since August, as he waits and waits for an explanation of what happened. He chartered a plane to fly Fink's body back to Port Vila and reported her death immediately to police, but a three-week investigation appears to have produced nothing.

Despite assistance from two of 10 Australian Federal Police officers stationed in Vanuatu, Nash says local police told him they did not even interview the sailors who sold Fink the MMS and who are still in Vanuatu. They have enlisted the product's creator to defend them in the court of internet opinion.

''Police enforcement is ... I don't know what to say. It's just not very well done,'' says Nash.

Noel Woodford, a pathologist from the Victorian Institute for Forensic Medicine, was summoned to Vanuatu to perform an autopsy on August 22, but the results have not been delivered.

There was nowhere in Vanuatu to cremate the body, so Fink's son, Joaquin, and Nash had to look to New Zealand. But local law requires bodies shipped out of Vila more than 24 hours after death to leave in a lead-lined casket, and they were asked to pay the Port Vila municipal council $US5500 ($5960) for a coffin. A $US1300 casket was located in New Zealand but prohibited, even though it conformed with Vanuatu regulations.

Without the more expensive casket, Fink's body would not be released. ''We felt like we were being conned,'' says Nash.

After negotiating the figure down to $US4500 and saying their goodbyes, Nash and his son-in-law learnt Fink's passport had been lost by Vila officials, making another trial of her repatriation to Mexico. Nash is staying in Port Vila until the autopsy results arrive. That means battening down the hatches until at least April, when equatorial storms have subsided.

In the meantime, he is helping out at the Department of Geology and Water Resources, improving the monitoring of active volcanoes.

People who drink MMS are consuming chlorine dioxide, a bleach added to drinking water and swimming pools and used to prepare some foods, such as flour. Because it is highly explosive, it must be mixed by adding citric acid to sodium chlorite from an MMS kit on site, before it is imbibed.

The product's American creator, Jim Humble, describes himself variously as a scientist, prospector and saviour of the human race who discovered the substance's powers while looking for gold in a South American rainforest in 1996.

In 2007, says the promotional blurb, ''this man heroically stepped out of the shadows to make this information and natural solution freely available to all humanity''.

''He believes the long-term availability of this substance ... may soon be heavily controlled by 'the powers that be'.'' At $US20 a bottle, Humble claims 200,000 Americans are now using it to cure everything from cancer to HIV to swine flu.

Nash, meanwhile, has spent his months in Vanuatu warning the world about Humble's elixir.

His letter to friends was published by a US magazine and on alternative health websites, sparking a cyberspace barney. Devotees swore by its healing powers. Critics linked it to other deaths.

Then Humble launched an extraordinary counter-attack online, saying Fink must have consumed more than the recommended dose, accusing Nash of hiding something and trying ''to destroy a chemical that is probably at this time the most important chemical that mankind has''.

He demanded that Nash be investigated. ''If I had the money I would pay for it to be done, but my money is, like I have always said, for the people here in Africa. If you think that is unfeeling, I am sorry. It is my job to protect MMS. Thirteen years ago, I stood in the jungle of Guyana and accepted the responsibility to take the cure that I had found to mankind,'' Humble wrote.

MMS is produced and available for sale online in Australia, but is not registered for sale.

Poisons and public health experts told the Herald that, in large doses, it can kill and that six people suffered adverse reactions to the drug in NSW last year, including three who were admitted to hospital.

A spokeswoman said the Therapeutic Goods Administration was investigating MMS, and the administration has found against some claims made by local distributors.

Humble's whereabouts is unknown. In an email to the Belgian sailor who sold Fink the MMS, he said he stays out of the public light because ''I have had threats against my life as there are those who do not want something that will replace drugs''.

The Vanuatu coroner, Rita Bill Naviti, was expecting the autopsy results around Christmas, but it is understood Woodford had to send samples to other laboratories and is awaiting those tests.

Joaquin Fink says he suspects MMS either killed his mother or reacted with her other medication to do so, but he is awaiting the autopsy results before forming conclusions.

The Herald does not suggest MMS was responsible for Fink's death.

Nash remains stranded in paradise. ''Some days I feel like an astronaut,'' he wrote recently, ''stuck in orbit, alone.''