THE past is a foreign country: they do things differently there," wrote LP Hartley in the opening paragraph of his acclaimed novel, The Go-Between. The unforgettable line set the tone for the fictional tale of Leo; a nostalgic elderly gentleman who reminiscences on the eventful summer in 1900 when, as a young boy, he dramatically lost his innocence.

Years on, the quotation's meaning still resonates with readers - particularly, it could be said, with those who have endured a traumatic loss of childhood and who continue to grapple with such memories.

When interviewing Loung Ung, a 36-year-old survivor of the Killing Fields of Cambodia, ahead of the launch of the second installment of her autobiography, entitled After They Killed Our Father: A Refugee from the Killing Fields Reunites with the Sister She Left Behind, I am immediately reminded Hartley's haunting words. So extraordinary and unimaginably brutal was Ung's childhood and introduction to adult life, that any existence must seem other-worldly.

In the first book, First They Killed My Father, Ung describes how until the age of five, she lived a stable, middle-class life in Phnom Penh, as one of seven children of a high-ranking government official and his wife.

Life was happy and comfortable until Pol Pot's Khmer Rouge stormed the Cambodian capital, forcing the family to leave virtually everything they had, assume different identities and latterly separate in order to survive. While Ung was trained as a child soldier (at only eight years old), the remaining members of her family were sent to work in labour camps. Her father, mother and two sisters, Keav and Geak, were eventually murdered by Khmer Rouge soldiers, while the other family members narrowly survived starvation and malnutrition.

In After They Killed Our Father, we rejoin Ung in 1980, then aged 10, as she leaves a Thai refugee camp, accompanied by Meng, her older brother, and Eang, his wife, for a new life in the US. In escaping the wreckage of Cambodia, they are also forced to say goodbye to Chou, their 12-year-old sister; their two brothers, Kim and Khouy; and members of their extended family. Settling in Vermont, the depleted family vow to return to their sister and brothers in five years.

Told in the first person, the book charts Ung's own Americanisation. This narrative interweaves with the recollections of Chou, who remained in Cambodia. Chou's life was initially hard; she missed her siblings and was living in a small, rural hut with her uncle and aunt and their five children. Much of her life was spent working the land, cooking, cleaning and looking after her nieces and nephews, although her aunt did allow her to go to school, providing she took her baby nephew, Nam, with her. In 1985, aged 18 years, she married Pheng, a local man, in an arranged marriage which, according to Ung, later "blossomed into love".

Ung's book makes for testing reading. It is at once moving and uncomfortable, but ultimately very hopeful. The catalyst for the second book came, says Ung, in her upbeat and friendly way, as she watched George Bush declare the end of the war in Iraq. "As I watched him declaring mission accomplished', I was so frustrated. Just because he said it war was over, it didn't really mean it was. For the victims of war, it never really ends. This second book is about trying to survive peace after war," she says.

I wonder what it takes to make sense of peace, and whether or not she has managed it. "It takes a lot to survive peace. Everyone has different journeys, but I think there are some commonalties. For one thing, it takes recognising the triggers, so you're not fighting the wars in your mind over and over again. For me, the war was physically over but it was ongoing in my mind.

"The slightest thing would trigger it off for me. The sound of a plane flying that bit too low; or the sound of fireworks, like bombs; or the cry of a child; or the rumbles in my stomach. I had no sense of what reality was for much of my early life, so I had trouble distinguishing what was war and what was real. Until I realised that these things just happen - like my stomach rumbling as a natural reaction - I would immediately think I was in the war situation again," she explains.

A difficulty in grasping reality, coupled with the horrific flashbacks of the war, continued to plague Ung throughout her teenage years. Some of the most moving parts of her work are when she describes the gravity of her depression and loneliness. She describes the unspoken rule which existed between her, Meng and Eang, prohibiting all talk "of Cambodia, the Khmer Rouge, Ma, Pa and especially Geak," and how enraged she was when people said how "lucky" she was for having gone through the revolution at such an early age. She writes: "They believe that my age means I'll heal faster, that I won't remember. They are wrong. I do remember, I just don't have the words to tell them about it. And that most of the time I'm silent about the war, it is never silent to me. It is always with me.

"As the chair rocks, I curl into the foetal position. It's Christmas. You should be happy. Everyone's happy on Christmas.' The sobs come faster now, pushing against my diaphragm and out of my throat. But I am so lonely.' I cover my hand over my mouth so Meng and Eang won't hear me. I don't want them to know. I miss my sisters,' I say out loud to the empty room. My chest heaves as I realise it's the first time I've said it, not just thought it. I miss Chou'."

Her family were not the only ones Ung hid her grief from. Recalling one visit to her school counsellor, Mrs Berringer, Ung writes: "I like Mrs Berringer. She possess a kind and maternal face. Still, I can't talk to her. The sadness is so unending, I fear it will swallow me up like a black hole. I'm afraid that if I let go and cry, I'll never stop. I want to tell Mrs Berringer there's so much pain inside me, that I'm lonely most of the time and scared a lot of the time. But I don't know how to make my mouth form the words I need to say. So I ramble about nothing."

Unsurprisingly, Ung's depression led to a suicide attempt. "I get out of bed and make my way to the bathroom. I'm just so sad,' I finally say out loud. And in forming the words something in me is released. In the bathroom mirror, the girl stares at me. Her eyelashes are wet, her face is haunting; she looks like the dead girl in my dreams. And the tears roll over me like waves in the ocean, they crash and pull me under," she writes. Later, Ung fills her tummy with painkillers. " I just wanna sleep,' I whisper. I miss them so much. The sadness is a black hole in my gut, a vacuum void that sucks all the light in," she writes.

In hindsight, did she really want to die? "I don't know if I was conscious of wanting to die, but I was very conscious of not wanting to live," she explains. "I just didn't want to feel that way any more. I wanted to sleep without nightmares for a very long time. I had held on to so many of the war memories because they were all the memories I really had. I felt I couldn't forget them until I made new ones. At the same time, I had a sense of wanting to hold on to them, painful and unpleasant as they were, because of the hopelessness I felt. I didn't know I was ever going to return to Cambodia or see Chou. It was a case of not forgetting my memories of my life in Phnom Penh until I had replenished them with new ones that I didn't want to forget.

"When I was reunited with Chou in 1995, I was able to move forward because I had created new memories and had found out that even though her life is so different to mine, she is happy. She is a mother and grandmother and I don't have have to feel guilty about what I have in life and what she doesn't have. She is where she is, and that's that. I don't have to try to make her life more like mine.

"It was such a joy to write the second book, and through it I learned to look at Chou not through the eyes of a Cambodian American, but a Cambodian woman," she says.

She aborted her suicide attempt, she says, for her nieces. "My mind went back to the scene in my first book where I imagined how my mother and youngest sister, Geak, were murdered by Khmer Rouge soldiers. Either one of them must have died seeing the other suffering or dead. I just couldn't do that to my nieces. I couldn't bear the thought of Maria trying to wake up my dead body. She was only five at the time, the same age Geak was when she was murdered in the Killing Fields."

TODAY, Ung, who is married and lives in Maine, travels to her native homeland at least twice a year in her capacity as a human rights worker. "Writing has been a way to exorcise the Khmer Rouge from my soul," she says. It is also her way of apologising to Chou. Chou wrote to me during college, but I never replied. I got caught up in leaving Cambodia behind and was busy living the American dream. I had built myself up to be a very successful woman, and had worked hard at doing so."

But on her first trip to Cambodia, that past finally caught up with her. On meeting her at the airport, a cousin remarked how her clothes resembled a Khmer Rouge soldier. "It froze me, and brought it all back. It showed me how I couldn't leave it behind as much as I wanted, or tried to. Since then, I have built new memories of life and joy. Now the old ones of death and suffering sit alongside the new ones, but that's OK. Right now, I'm pretty happy and stable," she smiles.

  • After They Killed Our Father, Mainstream Publishing, £12.99.

The Killing Fields: The tragic facts
From 1975 to 1979 through execution, starvation, disease and forced labour, Pol Pot's communist Khmer Rouge troops massacred an estimated two million Cambodians - almost a quarter of the country's total population.

On April 17, 1975, the Khmer Rouge stormed Cambodia's capital, Phnom Penh, forcing millions of the city's inhabitants to evacuate their homes and businesses.

The Khmer Rouge, or Angkar government, sought to create a pure utopian agrarian society, and to achieve this, its soldiers murdered thousands of teachers, doctors, lawyers, architects, civil servants, politicians, policemen, actors and other leaders. The wives and families of these "traitors" were also hunted and then killed.

Those who were not immediately killed by soldiers were gathered into crowded labour camps and forced to work for hours on end, seven days a week in the rice fields.

No matter how hard labourers worked, their only reward was more back-breaking work and starvation.