Fear that Nazi Germany might build an atomic bomb first drives the crash program that becomes the Manhattan Project, and this film reconstructs it through the people who actually built it. Robert Oppenheimer directs the scientific effort at Los Alamos, where plutonium production and the physics of the bomb itself move forward under tight security designed to keep even the workers from knowing the whole picture. Veterans of the project, including Ken Greyson, describe daily life at the base camp: its hurried construction, the secrecy drilled into every worker, and the strange detail of handing out welders' glasses so staff could watch the test flash without being blinded by it. Recollections rather than reenactment carry the story, with people who mixed chemicals or guarded gates recalling what they knew and what they didn't. The film stays close to the ground-level experience of the Manhattan Project rather than the political debates in Washington, tracing how an emergency wartime fear turned into the weapon that ended the war and started the nuclear age.