Vietnam: The Secret Agent is an investigation of the history, effects, and implications of the deadly compound "2,4,5-T," a main ingredient of the chemical weapon code-named Agent Orange, which the United States sprayed throughout Vietnam during 1961 to 1971. Its toxicological effects are still seen today, generations later: cancers, birth defects, physical deformities, deaths, contaminated soil in which dioxins bio-accumulate and concentrate in the food cycle. The chemical started as a herbicide in agriculture from the 1940s to 1970s, but was the first to be used in war, to similar effect. The film focuses on the exposure of these toxins to both citizens and soldiers alike, exposed through the lens of archival and battle-field footage, in support of interviews with veterans, scientists, attorneys and representatives of Dow Chemical--the company that made the chemical weapons--and the United States government, that used them against the world.