'My husband had always been active for the Tibetan cause so I suspected that he was doing something and wouldn't return, but I didn't want to stop him,' Lhamo Tso, 36, said by phone from India. 'He said to me that the most important thing was to make sure the children studied hard in India and got a good education.'

Lhamo Tso has four children: the eldest, her 16-year-old son, is from her first husband. With Dhondup Wangchen she has a boy, 12-year-old Tenzin Norbu, and two girls, Dadon Wangmo, 10, and Lhamo Dolma, who is eight.

Weeks later, Gyaljong Tsetrin, a cousin of her husband, called and told her the bad news.

Dhondup Wangchen, 34, had been making a documentary in Tibet on Tibetan attitudes to China's hosting of the Olympics and had almost certainly been arrested. The two cousins, close friends from childhood, had been working on the project together, with Dhondup Wangchen filming in Tibetan areas on the mainland and Gyaljong Tsetrin editing from Switzerland, where he has been living as a refugee since 2002.

Remarkably, the film tapes were successfully smuggled out of China, apparently just days before Dhondup Wangchen and Golog Jigme, his monk cameraman, were picked up by the police on March 26, Gyaljong Tsetrin says. They were on their way to Tongde county in Qinghai province, a Tibetan area in the northwest of the country, when they were detained. Just weeks earlier, violent anti-Chinese riots had broken out in Lhasa and spread across Tibetan areas in the west of China.

They were held initially at Ershilipu Detention Centre in Xining , the provincial capital of Qinghai. Later, Dhondup Wangchen was moved to Guangsheng Hotel, also in Xining, Gyaljong Tsetrin says. It is common for mainland police to detain suspects, particularly rights activists, in hotels.

But then, in July, Dhondup Wangchen managed to escape.

'The last time I spoke to him was March 25 and then nothing until July,' Gyaljong Tsetrin says. 'In the early hours of July 13 he called me again. He told me he had been held in a hotel but had escaped [from] the guards under the cover of darkness. He said he had no money, nothing, and could I send him some money. I told him to hide out in the countryside and come back in two days when I would have money ready for him.'

Dhondup Wangchen described to his cousin how he had been mistreated in detention.

'He said he had been interrogated and interrogated,' said Gyaljong Tsetrin. 'He told me he had been tied to a chair for four days straight. When he spoke to me on the phone he said his hands were still buzzing and numb from being beaten.'

But then Dhondup Wangchen disappeared once more. Gyaljong Tsetrin believes he was arrested again. He said sources had also told him that cameraman Golog Jigme was being held in a detention centre in Linxia , in Gansu province. To date, the authorities have not acknowledged that they are holding either man.

Gyaljong Tsetrin took the hours of film Dhondup Wangchen had recorded and trimmed it down into a 25-minute documentary called Leaving Fear Behind.

'We wanted to make a film that would give Tibetans a voice,' he explains. 'Tibetans in Tibet are struggling to get their voices heard but it's very difficult for them to get their message out. And, with the Olympic Games coming, we thought a film would be more long-lasting and more effective than any demonstration.'

There's no doubt that Leaving Fear Behind is a propaganda film - everyone interviewed is unequivocally anti-Chinese. Dhondup Wangchen, himself, expresses his wish to the camera that Tibetans should fight together for greater autonomy in Tibet - the so-called 'Middle Way' supported by the Dai Lama.

But when Dhondup Wangchen turns the camera on a group of aged Tibetan nomads, the documentary becomes genuinely moving.

One old man dressed in a thick traditional smock starts sobbing pitifully as he talks about his feelings for the Dalai Lama.

'For the Dalai Lama to come back is my greatest wish and dream,' he weeps, his body crumpled and his head bowed. 'I only have to hear his name and I am filled with faith, devotion and deep, deep sadness. The situation is hopeless.'

It is dangerous for Tibetans to openly express opposition to Beijing rule. Those who did so in this documentary risked their own freedom. Gyaljong Tsetrin says he has heard unconfirmed reports that several of the people who appeared in the film have been detained and questioned.

'If the 2008 Olympics Games take place then they should stand for freedom and peace,' says a monk on an empty highway in the film. 'As a Tibetan I have neither freedom nor peace. Therefore I don't want these Games.'

The film was screened to journalists in Beijing just days before the Games began and again last month to the United Nations Human Rights Council in Geneva. It's available online on Google video, and so far it remains unblocked on the mainland, although the Leaving Fear Behind website has been off limits since August.

This is not the first time Dhondup Wangchen has been in trouble with the police. He had been arrested at least twice before in connection with activist work, and both times was held for several months.

He was fully aware of the risks he was taking, says Gyaljong Tsetrin. 'But he felt they were worth it. He always had very, very strong views about China and what the Chinese government was doing in Tibet and he was always happiest when he was doing something that would benefit Tibetan people or the Tibetan cause. I feel very sad about what happened to him. We are closer than brothers.'

Dhondup Wangchen was born into a farming family in Qinghai. The two cousins grew up together. They escaped to India in 1993 to see the Dalai Lama before returning to Tibet to live in Lhasa. Gyaljong Tsetrin ran a restaurant, which became an impromptu meeting place for Tibetan rights groups. They were both fired up with dreams of freeing Tibet from what they saw as Chinese repression.

Lhamo Tso remembers her husband's passion. 'When we lived in Tibet, he used to say that Tibetans should be the ones in charge. He disliked what he saw as more and more Chinese people settled in Tibet year after year,' she says.

'He couldn't stand Tibetans being taken advantage of by the Chinese and wanted Tibetans to at least be equal with Chinese people.'

The big question now is what charges will be levelled at him.

'Making this film meant that Wangchen had contact with people outside of China so the Chinese could bring about some very serious allegations,' says Gyaljong Tsetrin. 'I'm worried what they will accuse him of ... maybe something to do with stealing state secrets or splitting the motherland.'

Ngawang Choephel, a Tibetan music scholar was arrested in 1995 for making a documentary on Tibetan music and dance. He was convicted of espionage and sentenced to 18 years in prison, and was only released after Washington put pressure on Beijing six years after his arrest.

'All political prisoners go through the same experience of both physical and mental torture,' Ngawang Choephel said by phone from the United States, where he now lives.

'China controls the climate of Tibetan people's life. Sometime it's cold, sometimes it's hot, sometime it's sunny but most of the time it's dark and cloudy.'

For Lhamo Tso, it's a struggle looking after four children in a foreign country far from home and without her husband.

She gets up in the early hours of the morning to bake bread to sell to make money for the family. Even so, she says, she is not angry at him for leaving her.

'I feel extremely proud of what he has done. I think his film is a great achievement for Tibetans in Tibet,' she says. 'He is a great father and the children love him very much. They miss him a lot and we talk about him every day.'