HOUSTON --She's described as a no-nonsense negotiator representing the largest teachers union in the state. But before being an advocate for teachers, Gayle Fallon had another identity, a secret identity. Fallon is known as a fighter for teachers. As president of the Houston Federation of Teachers, she's used to giving an earful to the HISD superintendent and board of trustees. But over 40 years ago, Fallon was fighting a different battle. "When I worked there, we were not allowed to tell people who we worked for," Fallon said. Fallon worked as a code breaker for the National Security Administration. With a top secret classification, Fallon translated and broke coded communications captured during the Vietnam War, a process, that in 1966, meant lives were at risk every minute it took to break the enemy code. "Every one of us had an experience when we walked away from one -- and then came back and translated it and missed the attack," Fallon said, "And at that point, you sit there and go, oh my God, there are people that died because I took an extra half hour." A haunting image, Fallon says, that took decades to reconcile. "It took a long time before I could go to the wall, because I didn't know if I was responsible for any names on it," she said. Her incredible journey started in the summer of love, while students were protesting in the street. Fallon was a newlywed and a student at American University when she was recruited by the NSA. A crumpled certificate shows she earned 'Basic Vietnamese Reading,' an accomplishment that wasn't her idea. "They came up with the idea of language school, and I pointed out my language aptitudes are not great, and they pointed out they didn't care," Fallon said. She says she sat in class eight hours a day for six months and learned Vietnamese. Meanwhile, the NSA kept close tabs on who she socialized with, as well as other aspects of her life. "They asked if my sex life was satisfactory," Fallon said and laughed. "I said, 'Yeah, I'd been married for a year. It's fine. We're still getting along.'" But it was her top secret job that also bothered her. Fallon did not support the government's war effort and troop escalation. She quit after two years. Fallon, like so many young people of the day, expressed her feelings by writing songs. Today, she's a devoted grandmother and dog lover. She's also learned to deal with lingering guilt from her days as a code breaker. "You can only sit there and balance it with the lives you saved, because when we could predict an attack, we saved a lot of lives," she said. Times and technology have changed since the 60s. Much of the work Fallon did as a code breaker is done now with computers. And there's still a lot from those days she still can't talk about because the information may be classified.