In the late 1960s, filmmaker Sandy Northrop was a hippie who participated in campus demonstrations against U.S. involvement in Vietnam.

Now she lives in that country and has produced a film about a man who helped wage that war. Her documentary, "Pete Peterson: Assignment Hanoi," airs Thursday at 10 on WETA and at 11 on MPT.

Air Force Capt. Douglas "Pete" Peterson was on his 67th mission when his F-4 Phantom fighter-bomber was shot down by the North Vietnamese in 1966 near the port city of Haiphong. Imprisoned for 6 years, he was held in solitary confinement at various places, including the infamous "Hanoi Hilton," and repeatedly interrogated and tortured.

Thirty-one years after he was captured, he returned to Hanoi as the United States's first ambassador to Vietnam since the fall of Saigon in 1975.

Peterson's official mission is to mold a positive, lasting relationship with his former enemies and establish a trade agreement with the United States. But Northrop believes his is what she calls "a message of reconciliation." And that continues to amaze her.

"How could a guy forget about all the horrible things he suffered and move forward?" she recalled thinking. "That was my question, always: How do you focus on forgiveness? Forgiveness -- it's the hardest concept. But what he continually said was, `You can't spend your time looking backwards.' "

As a film historian and editor, Northrop had specialized in finding archival footage for television productions such as PBS's National Memorial Day Concert. She had seen plenty of film of emaciated POWs. "I knew more or less what they'd gone through," she said in an interview from Hanoi.

She had also seen footage of the visit to Hanoi by actress Jane Fonda who, confronted with American prisoners of war, seemed in news reports at the time to side with their North Vietnamese captors. Back home, angry veterans branded her "Hanoi Jane." The POWs, Northrop learned later, had been forced by their guards to appear.

Northrop herself had been opposed to the United States's involvement in Vietnam in 1969 when she was a student at the University of Michigan.

"We were naive, the anti-war movement was naive," she says now. "I mainly opposed the war -- the war was wrong -- but I never pursued it beyond that. I think it was an innocence. . . . Your whole life was defined by the friendships you had. What we were thinking about was us as a social movement. I think there was a hard-core 5 percent that was really committed and really understood, but for 75 percent of us, it was just a social thing.

"It was only as I became older that I began to pursue it in a real sense. At age 50, you have perspectives that are different from when you were 22. You need to see the wide spectrum, the history of the Vietnamese."

In one of life's strange twists, 2 years ago Northrop found herself heading to Vietnam with her husband, Los Angeles Times reporter David Lamb, who was assigned to cover Southeast Asia. When they learned they would be living in Hanoi, Peterson was undergoing confirmation hearings and would report for duty on May 9, 1997, just before Northrop and Lamb arrived.

"Within two weeks we were invited to go to one of the MIA sites with Ambassador Peterson," said Northrop, referring to a location where the remains of U.S. servicemen were found. "I thought, This is an opportunity to see whether when the lights go off, he's still there. And he was still there. He was still 100 percent committed to going forward."

Northrop decided she wanted to tell the remarkable story of a man who had every reason to be bitter, but who instead returned to try to forge diplomatic and trade agreements between his country and the one that had been his enemy.

After Peterson was freed, he spent 26 years in the Air Force, 10 in the contracting and computer businesses and six as U.S. Representative from Florida, co-chairman of the U.S.-Russian Joint Commission on POW/MIAs. He was a 61-year-old widower when he went to Hanoi as ambassador.

Not long after Northrop met Peterson, she asked to make a documentary of his life. Her husband would do the narration.

"He thought that someone was going to make a film about him," she explained. "And I was living here, unlike any other film team that would come in for a month or a short period. I really could stay in there for the thick and thin of it, and I think that appealed to him. There's this moment when you finally cross over the threshold. I was thrilled when he agreed."

Filming Peterson turned out to be the easy part; the State Department was a different matter. "There were a lot of hurdles I had to jump over in order to do an honest piece," she said.

State Department officials were concerned about what would be shown in her documentary, about picturing the embassy and the ambassador's residence, about recording the ambassador's day-to-day routine.

"They were saying, `Don't show this, don't show that,' " she said. "So I lived within those restrictions."

Then on Aug. 7, 1998, two months after Northrop finished filming, U.S. embassies in Kenya and Tanzania were bombed, killing 224 people.

"I have to say for them that their concerns about security at the embassies was justified," she said.

To make her film, Northrop used a small, unobtrusive, digital-format camera to shoot nearly 60 hours' worth of footage over four months. "They don't even look at these cameras," she said."

Peterson's story included a romance. At an Israeli Embassy party shortly after his arrival, Peterson met Vi Le, 40, an Australian diplomat. Her family had left Saigon when she was an infant and lived in Laos, Hong Kong, Thailand and France before settling in Australia. She attended college there, became a banker and then was named that country's senior trade commissioner to Hanoi. She never had married.

The American ambassador and the Australian diplomat were married a year later, in May 1998. It was the last event Northrop shot for her film.

"We used two cameras that day," she said. "It must have been 110 degrees -- the sweat that ran down Ambassador Peterson's face was not from nervousness. In fact, it was so hot that the candles on the altar actually melted."

About 200 guests attended the wedding at Hanoi's Roman Catholic cathedral. A red carpet ran from the street to the altar. The Vietnam National Symphony played Beethoven's Symphony No. 7. Peterson's son Michael traveled from Florida to attend.

"I don't think he ever thought he would fall [in love] again," said Northrop. "He thought he was going to be alone. But to see him now, this friendship . . . they share so much, they have this kind of energy."

In June, Vi Le Peterson retired from diplomatic service to start a consulting business, said Northrop.

Meanwhile, Northrop, having hired cameraman Tran Le Tien to help her conduct interviews for her documentary, has begun language lessons.

"It's a hard language, but it was apparent to me that whatever I do next, I needed it," she said. "We'll be here another year and a half, and I plan to do several more films."

She also has learned more about herself: "You have to look the North Vietnamese people in the eye and say to yourself, `No different from me.' "

And there was one other revelation: "The most incredible thing for every American coming here to learn is that the Vietnamese don't hate us," she said.

"When we first got here two years ago, we went out and hired a car one day. The driver had been with the North Vietnamese army and still has a bullet lodged in his chest.

"He said, `You're Americans and we fought you for 10 years, and before you there were the French and we fought them for 100 years and before them, the Chinese, and we fought them for 1,000 years. We're a very proud people, and you're a very small part of our past.' "