J. Robert Oppenheimer led the Manhattan Project that built the first atomic bomb, then spent years afterward arguing against building something far more destructive: the hydrogen bomb, or "superbomb." This episode of the series follows that fight inside the American government, as Oppenheimer's calls for international control of nuclear weapons put him against military and political figures who wanted the bomb built as fast as possible. Archival footage and expert interviews sit alongside dramatic reenactments, with Joe Jones and Shannon Whirry playing Oppenheimer and his wife Kitty, and narration from Sean Pertwee carrying the story through the Cold War brinkmanship of the early 1950s. The episode traces how Oppenheimer's opposition cost him his security clearance, ending his access to the program he had once led, and treats that downfall as the direct price of his position. It sits within a five-part series on the nuclear arms race, moving from the first bomb through the Cuban missile crisis and nuclear proliferation in the Middle East.