Children's laughter wafts over the fence from a prismatic schoolyard in the distance as I stand in the Killing Fields of Choeung Ek. It eases the tension of this haunted place to know that, through it all, life carries on. Choeung Ek looks no different than any other field. Before the Khmer Rouge turned Cambodia upside down, Choeung Ek was an orchard of longan fruit. Even today, butterflies buzz about the rolling fields, belying the horror that lies beneath.

They say that every time the rains pound Phnom Penh, bones rise from the ground at Choeung Ek.

In order to save bullets, The Khmer Rouge beat their victims to death. After placing the bodies in mass graves, soldiers poisoned the ground to ensure that no one survived. So, while the Killing Fields may look like any other field, the ground itself is toxic.

Babies were beaten to death at the mammoth bashing tree. Women were shaved bald and disposed of. Other burial sites reveal piles of decapitated skeletons. The crimes against humanity that occurred at Choeung Ek are unfathomable.

A white stupa stands tall in the center of the field, shelving the bones from excavated sites at Choeung Ek. The sheer amount of skulls glowering out of the structure gives weight to its exclamatory form.

The majority of these sad souls arrived from Tuol Sleng prison in Phnom Penh, a torturous institution that no high-ranking Khmer Rouge official claims any knowledge of. Before the Khmer Rouge stormed into Phnom Penh liberating the people and evacuating the city, Tuol Sleng was S.21, an unassuming three-story schoolhouse in the heart of the town. Within weeks, it was made-over into the most notorious prison in Cambodia. Pull-up bars became torture devices as school rooms were converted to cells. Locked inside S.21 were the rich and the famous, the élite and the educated, the opposition and the ethnic - anyone who was anything in the old Phnom Penh was a threat.

A movement that arose in the countryside, the Khmer Rouge distrusted anyone from the city. Feeding on anti-American sentiment over bombings that bled across the border from Vietnam, they ousted the pro-American regime of Lol Nol. Making their final ascent into Phnom Penh, the Khmer Rouge claimed that the entire country was liberated and marched Cambodia back into the Stone Age. Abolishing religion, education, and government, they imprisoned every citizen. Families were torn apart and sent to work in camps, manning the fields of rice.

Cambodia's cities became ghost towns and its people wandering spirits.

Pol Pot and his men effectively orchestrated the most horrific genocide in living history. Starved, beaten, and killed, over the next four years, the Cambodian population was reduced by one-third at the hands of its own countrymen.

As I pace though the ground floor of S.21 (Tuol Sleng) the pleading eyes of its former residents search for justice. Photographed and documented at intake, the haunting black-and-whites are organized in overwhelming checkerboard displays on schoolroom bulletin boards. The women appear stripped of their sexuality with cropped hair and vacant eyes. The men, with gaunt, angular faces, gaze out in wild-eyed frustration. Of the thousands who slept in this schoolhouse jail, just seven survived. The men and women on these walls are the faces of Cambodia's ghosts.

In the late 1970s, the people of Cambodia were split and torn against each other. The Khmer Rouge preyed on the rural poor who, uneducated and with little alternatives, turned to the rising movement. Their stories find a voice in S.21 as well. In a series of then-and-now photos of former Khmer soldiers, those who survived speak of returning to their villages to piece together the life they lost to the movement.

S.21's top floor explores the continued search for justice for the Cambodian people. Remarkably, Pol Pot was never held accountable for his crimes against humanity and died in 1998 a free man. The Khmer Rouge even held Cambodia's UN seat for twelve years after the Vietnamese invasion ended their rule.

The end of the Khmer Rouge period in 1979 led to a civil war that finally ceased in 1998 when the Khmer Rouge's political and military structures were dismantled. Yet, even today, the party remains in remote pockets of the rural north.

As I return to S.21's courtyard, the blazing afternoon sun shoots past the former prison's elegant palms. I step back out into Phnom Penh's chaotic streets to the cries of disfigured and destitute beggars. A one-legged man is selling his survivor story. A blind woman pawns hers. My tuk tuk driver ushers me away, recommending a side trip to Thunder Ranch, a shooting range near the Killing Fields where eager tourists fire AK47s or rocket launchers and chuck grenades at local livestock. He opens up the pamphlet with an earnest smile, oblivious to how I might react to this proposition after leaving his country's most brutal prison.

Most Cambodians would rather move on than dig up their ugly past. Some don't acknowledge anything happened at all. In 1997, the government requested that the United Nations assist in establishing a trial to prosecute the senior leaders of the Khmer Rouge. In 2001, the Cambodian National Assembly passed a law to create a court for trying serious crimes committed during the Khmer Rouge regime 1975-1979. This court is called the Extraordinary Chambers in the Courts of Cambodia for the Prosecution of Crimes Committed during the Period of Democratic Kampuchea (or ECCC). In 2006, the ECCC organized a trip for all Cambodians to visit S.21, the Killing Fields and other sites to come to terms with their past and give invaluable testimony for the trial.

Last July, in the tribunal's first case, Khmer Rouge official Kaing Guek Eave was sentenced to thirty-five years in prison for running the notorious S.21 prison. As you read this, case 002 is under way. In total, there will be four hearings. Justice for the Cambodian people is, at long last, a possibility.

A walk through Phnom Penh is a tornado trip through dark alleys and pools of light, stoic monasteries and lavish gardens, riverside flair and backstreet fear. Some parts of the city, with seedy flophouses, rampant drugs and prostitution, feel like a heroin nightmare. Others offer a glimpse of the country to be. The city itself cuts abruptly to rice fields at the edge of town, a stark reminder of Cambodia's dueling personas

The Khmer people were once at home in one of the world's greatest civilizations. Now, they live in the poorest country in Southeast Asia. It's amazing what four years in the hand of an evil regime can do to a country.

Phnom Penh is bleeding bones, but it is also swarming with butterflies.

These fluttering rainbows mark the beginning of a magnificent metamorphosis. Their flashy coats offer a glint of beauty - a welcome change, masking the wormy scent of a foul past.