Zheng Rui's mother and father greet her as she walks down a lane toward her home after a long day at work. Zheng has kept this heart-warming picture in her mind for the past five years.

"They used to stand in front of my building, smiling and waving at me," said Zheng, a researcher at the cancer center of Johns Hopkins University in Baltimore, Maryland. But every time she sees it, the agony returns.

Zheng's parents, Zheng Yuguang, 65, and his wife Yang Shuyin, 62, were on board American Airlines Flight 77 to Los Angeles on September 11, 2001, as it crashed into the Pentagon.?

Five years on, the memory remains a distressing one for Zheng, who refused to recall the details of that day during a telephone interview with China Daily. "It was just too much sorrow to begin with," she explained. "I've tried hard not to think about it. So do people around me. The accident had such a huge impact that it changed my life and my attitudes toward life forever."

Prompted how it affected her decisions in daily life, she would give no clear answer: "I cannot say exactly how. Maybe in 10 years, I'll be able to sit down and make a list. But not now."

The turning point of Zheng Rui's life came in 1999 when she went to the US from Beijing to strive for a post-doctoral degree from Johns Hopkins. Before long, she invited her parents, both retired in Beijing, to visit her and stay for almost a year.

Zheng Yuguang, a former chemist, and his wife, a retired pediatrician, were married for 35 years. They also raised a son, Yang Shidong, who works at Fujitsu electronics in Nagano, Japan.

The memories of their visit to the US are still sweet and joyful.

"Unlike Western parents, my parents didn't say 'I love you,' but their love was reflected in their everyday lives," Zheng said. "I still miss their witty jokes and my mum's cooking."

Her parents enjoyed their time in the US. Zheng Rui and her husband, Wan Li, took them traveling, hiking and swimming in Maine. During their stay, the elderly couple reached out to the local community, revealing their zest and passion for life, Zheng recalled.

"It was amazing that they made some good friends here, although their English was very limited," she wrote in an online obituary.

"Although they were over 60, they were still enthusiastic about learning English. When a word came up, they would immediately turn to the dictionary or ask me."

Before boarding Flight 77, Zheng Yuguang and Yang Shuyin told their daughter, who saw them off at Dulles Airport, how much they had enjoyed the year with her and promised to visit again in a couple of years. Then they hugged and kissed her and disappeared into the airport.

When news of the 9/11 attacks reached China, their Chinese relatives could not believe it.

"It was surreal," said Chen Wei, Zheng Rui's cousin in Changzhou of east China's Jiangsu Province, of their first reaction. "We?would never have thought that the two of them were on the plane. There was more chance of winning the lottery than of being attacked by terrorists."

When the deaths were confirmed during a call from Zheng Rui, relatives in Changzhou were shocked, their grief mute. On the phone, Zheng Rui cried and couldn't continue the conversation, Chen recalled. For Yang Shuzhen, the sudden death of her beloved younger sister was unbearable. Chen said: "My mother collapsed and felt her heart break after hearing the news."

Chen attended the funeral, held in Washington D.C., on behalf of the family. All procedures for the trip were quickly green-lit and completed in only three days.

Chen was impressed by how well the US government took care of them. "Everything was well-arranged," recalled Chen, 45. The US government bought her a first-class ticket. A guide and an interpreter accompanied her throughout the five-day trip. At the memorial service at the Pentagon, Chen joined other family members, gathering for the first time after many years of separation, to share their grief with relatives and friends.

"There was a whole floor in a building in Washington, displaying pictures of the deceased," Chen recalled.

At the memorial site, people talked and offered condolences, many without knowing each other's names. "I met people of many different colors," Chen said. "The tragedy bound everyone into one big family."

At the Pentagon, Zheng Rui and her family called out the couple's names in hope that her parents' spirits would hear. Zheng took some earth from the Pentagon and later buried it at a cemetery in Beijing.

"She wanted them to rest in peace at home," Chen said. However, Zheng Rui cannot share in that peace, a sense of guilt shadowing her. She sometimes asks herself: "What if they hadn't come to visit me? Would they still be alive and living a happy retirement in China?"

Most of all, the pain of being unable to see her parents never ends. "It just exists at different stages," she said. "It is not an ordinary wound. A knife wound will heal one day. But this wound will never heal, and the grief will follow me for the rest of my life."

Today, a 30-minute event in Washington organized by the US Congress will commemorate the foreign victims of the 9/11 attacks. A third Chinese person, Michael Gu, 34, of Shanghai, also died, at the World Trade Center in New York. His widow, Jean Liu, declined to be interviewed.

Zheng was invited to be a keynote speaker and will also read the names of the countries where the foreign victims came from. She said: "It is an opportunity for me to let more people know my parents, who were loved by their families and friends."

(China Daily September 11, 2006)