Thet Sambath is a newspaper journalist in Phnom Penh. He is also one of millions of Cambodians whose loved ones were killed or disappeared during the Khmer Rouge's murderous reign of the 1970s.

Sambath's personal mission for more than a decade was to find out the truth about the genocide which still haunts his country and it was a labour of love which has produced astonishing results.

This incredible film documents his efforts since 2006 when he realised he ought to start recording the interviews he was conducting and teamed up with co-director Rob Lemkin.

Sambath managed to persuade not only low-ranking members of the regime to talk on film about how they came to kill so many but also the most senior surviving leader, Nuon Chea.

In the case of Pol Pot's right-hand man aka Brother Number Two Sambath met with him for five years before he even began to talk about what really took place.

The reporter gained Chea's trust, visiting him regularly at his home without revealing his own heartbreaking losses: the murder of his father in 1974, the death of his mother in childbirth in 1976 after she was forced to marry a Khmer Rouge militiaman and the disappearance of his brother in 1977.

Sambath's patience paid dividends, as the testimony he elicited from the elderly Chea now awaiting trial for crimes against humanity displays.

Brother Number Two's answers to Sambath's quiet but insistent questioning belie everything he has previously told journalists about his part in the genocide.

Just as compelling is the evidence of peasant farmers Khoun and Suon between them responsible for the deaths of many Cambodians.

They were at the bottom end of the food chain, following orders from above to kill those considered "enemies of the people".

Sambath somehow manages to persuade them to talk about their actions, to show him the location of scores of bodies and even to demonstrate exactly how they killed.

It is awful to watch but fascinating. The camera catches every emotion etched on their faces as they tell their stories: pain, shame, embarrassment and, undoubtedly, relief.

Sambath's own expression as he listens to Khoun and Suon, as well as Chea is just as interesting. He displays none of the rage or thirst for revenge that one might expect.

He just gently probes his inHe just gently probes his interviewees to finally tell all and calmly accepts the shocking details when they do.

His role in the story as a journalist determined to document the truth about his country and as a victim of the evil perpetrated by the Khmer Rouge makes this more than a movie about the Killing Fields.

It is a film which gets to the heart of human nature the very worst of it, and the best.

'Enemies of the People' will screen tomorrow at 4.15 p.m. at the Bermuda Underwater Exploration Institute.