Williams: After two decades of terror, the tide is turning for one of humanity's most brutal ever regimes.
One place you can see the change is here, on the road to the coastal town of Kep.
Just a few months ago, regular raids by Khmer Rouge guerillas made it dangerous for Cambodians, impossible for foreigners. Last time I was here, three foreigners, after having been kidnapped from this train, had just been murdered by the Khmer Rouge.
But the government had also cut a secret deal to end the guerilla threat, by getting a senior guerilla commander to defect with several hundred fighters and their families.
Now, just outside the town of Kep, no longer living in the jungle as rebels, we find the family of the key defector, Colonel Chouk Rinh.
Chouk Rinh's wife looked after the hostages on their first day in Khmer Rouge hands.
Mrs Rinh: I had no say in this. I didn't know what to do, I opened the door and saw three foreigners who'd been taken captive. I cooked some food for them. The next night Commander Paet took them away.
Williams: She later played a key role in the defection. The government took her to a hairdresser in Pnomh Penh. She went back to the jungle and told her husband to change sides.
Mrs Rinh: Commander Paet was angry because he saw me going to Pnomh Penh. He was angry, that's why he killed them.
Williams: Finally, we find the man at the centre of the defections, Colonel Chouk Rinh, the former Khmer Rouge commander, who took the hostages from the train.
Rinh: When we attacked the train, it was my men and Paet's, but we didn't know there were foreigners on board.
Williams: He says he knew nothing of the hostages' fate when he joined the government ranks, promising to help save the foreigners.
Rinh: Paet sent someone over to my place to get the foreigners. Until I heard they'd killed them I knew nothing. When I defected I thought the foreigners were still alive.
Williams: Anywhere else he'd be charged with kidnap and complicity to murder. Instead, he's been made a government officer for clearing this area of guerilla war.
Down the same road he used to plunder, Chouk Rinh takes us to the field that's meant to be the defectors' new home. A dirt track is being pushed into their former jungle stronghold.
With this patch of dry scrub the foundation of their new life, it's easy to see how some may be tempted by the free wheeling days of banditry and the gun. But the former guerillas say they will not go back to the Khmer Rouge.
Rinh: We trust the government We trust the guys we used to fight.
DAVID ASHLEY, Author, former Govt. Advisor: The leadership is old. The main leaders, Pol Pot, Nun Chi, Ta Mok, are all in their late sixties, early seventies. They can't continue for too much longer. When those people die off, specifically Pol Pot, Brother Number One, Uncle Number One, Uncle Eighty-seven, or whatever you want to call him, then they won't have any coherence left.
Williams: Only recently isolated, and under Khmer Rouge control, villagers here are now receiving aid. It may look like something from Pol Pot's killing fields, but this time the people are smiling. They're getting paid in rice to rebuild this vital irrigation system - foreign aid that until very recently could not reach here.
We head further north. Only months ago, it was totally off limits, guerilla country.
These rough and ready guerillas used to be one of this region's most ruthless Khmer Rouge units. Their commander's decision to defect makes them the latest prize in a program that's brought to the government some four thousand Khmer Rouge fighters.
The Khmer Rouge fighting force is thought to number just six or seven thousand, well down from the ten or fifteen thousand estimated during the elections. This Khmer Rouge commander defected with his men when his leaders ordered them to burn villages in which they had relatives.
Pichmonyl: I don't understand the Khmer Rouge. They ordered me to burn the houses, and I refused. That's why I came across to the government.
Williams: For many, the choice between the Khmer Rouge and the Government is not a matter of ideology.
It's economic. And at the moment a life with the government, as basic as it may be, is better.
Cambodia's making the first steps towards recovery. But some warn without proper controls on government corruption the new investment could be a double edged sword, playing into the Khmer Rouge hands.
Critics say more than half of Cambodia's foreign investment is in casino and tourist resorts, not the industry or infrastructure needed to give Cambodians jobs and a future.
Pol Pot's central organisation is yet to fall. And while the defections reveal a fundamental crack in the Khmer Rouge armour, the Government must curb its own abuses, while providing a better life for Cambodians.
One place you can see the change is here, on the road to the coastal town of Kep.
Just a few months ago, regular raids by Khmer Rouge guerillas made it dangerous for Cambodians, impossible for foreigners. Last time I was here, three foreigners, after having been kidnapped from this train, had just been murdered by the Khmer Rouge.
But the government had also cut a secret deal to end the guerilla threat, by getting a senior guerilla commander to defect with several hundred fighters and their families.
Now, just outside the town of Kep, no longer living in the jungle as rebels, we find the family of the key defector, Colonel Chouk Rinh.
Chouk Rinh's wife looked after the hostages on their first day in Khmer Rouge hands.
Mrs Rinh: I had no say in this. I didn't know what to do, I opened the door and saw three foreigners who'd been taken captive. I cooked some food for them. The next night Commander Paet took them away.
Williams: She later played a key role in the defection. The government took her to a hairdresser in Pnomh Penh. She went back to the jungle and told her husband to change sides.
Mrs Rinh: Commander Paet was angry because he saw me going to Pnomh Penh. He was angry, that's why he killed them.
Williams: Finally, we find the man at the centre of the defections, Colonel Chouk Rinh, the former Khmer Rouge commander, who took the hostages from the train.
Rinh: When we attacked the train, it was my men and Paet's, but we didn't know there were foreigners on board.
Williams: He says he knew nothing of the hostages' fate when he joined the government ranks, promising to help save the foreigners.
Rinh: Paet sent someone over to my place to get the foreigners. Until I heard they'd killed them I knew nothing. When I defected I thought the foreigners were still alive.
Williams: Anywhere else he'd be charged with kidnap and complicity to murder. Instead, he's been made a government officer for clearing this area of guerilla war.
Down the same road he used to plunder, Chouk Rinh takes us to the field that's meant to be the defectors' new home. A dirt track is being pushed into their former jungle stronghold.
With this patch of dry scrub the foundation of their new life, it's easy to see how some may be tempted by the free wheeling days of banditry and the gun. But the former guerillas say they will not go back to the Khmer Rouge.
Rinh: We trust the government We trust the guys we used to fight.
DAVID ASHLEY, Author, former Govt. Advisor: The leadership is old. The main leaders, Pol Pot, Nun Chi, Ta Mok, are all in their late sixties, early seventies. They can't continue for too much longer. When those people die off, specifically Pol Pot, Brother Number One, Uncle Number One, Uncle Eighty-seven, or whatever you want to call him, then they won't have any coherence left.
Williams: Only recently isolated, and under Khmer Rouge control, villagers here are now receiving aid. It may look like something from Pol Pot's killing fields, but this time the people are smiling. They're getting paid in rice to rebuild this vital irrigation system - foreign aid that until very recently could not reach here.
We head further north. Only months ago, it was totally off limits, guerilla country.
These rough and ready guerillas used to be one of this region's most ruthless Khmer Rouge units. Their commander's decision to defect makes them the latest prize in a program that's brought to the government some four thousand Khmer Rouge fighters.
The Khmer Rouge fighting force is thought to number just six or seven thousand, well down from the ten or fifteen thousand estimated during the elections. This Khmer Rouge commander defected with his men when his leaders ordered them to burn villages in which they had relatives.
Pichmonyl: I don't understand the Khmer Rouge. They ordered me to burn the houses, and I refused. That's why I came across to the government.
Williams: For many, the choice between the Khmer Rouge and the Government is not a matter of ideology.
It's economic. And at the moment a life with the government, as basic as it may be, is better.
Cambodia's making the first steps towards recovery. But some warn without proper controls on government corruption the new investment could be a double edged sword, playing into the Khmer Rouge hands.
Critics say more than half of Cambodia's foreign investment is in casino and tourist resorts, not the industry or infrastructure needed to give Cambodians jobs and a future.
Pol Pot's central organisation is yet to fall. And while the defections reveal a fundamental crack in the Khmer Rouge armour, the Government must curb its own abuses, while providing a better life for Cambodians.