Last month, Mr Lee Ellis stood in front of the infamous Hoa Loa Prison in Hanoi, overcome by a maelstrom of emotions.
The place holds dark memories for the war veteran. As an American fighter pilot during the Vietnam War, he was tortured and imprisoned there for 51/2 years after his F-4C Phantom was shot down and he was captured on Nov 7, 1967.
His trip last month was the first time in 41 years that he had gone back to Vietnam, and to the place he calls the pits of hell.
As Mr Ellis, 70, and his wife were about to enter the premises - now a war museum - the authorities stopped him from bringing in his video camera because it "looked too professional".
Arguing that he had a letter allowing him to do so cut no ice with the staff. "It just set me off, and brought back all the fear and sense of oppression and control," he says.
Once he was inside the building, his discomfort grew. Many of the cells where prisoners of war (POWs) were tortured were gone. There were, instead, exhibits and pictures showing how well American soldiers were treated.
"I feel a lot of resentment because of the lies told. Every time a lie is told, it undermines freedom. You need truth for freedom to really exist," says Mr Ellis, who stopped over in Singapore after his Vietnam trip.
Although frustrating, he says, the trip reminded him that he has to persevere with what he has set out to do. "I probably understand the importance of truth and the danger of lies better than the average person, and I want to challenge others to live the truth."