This episode dramatises the minute by minute events leading up to the world's first ever atomic bombing. Based on extracts from President Truman's personal diaries which show the decision-making process reflecting America's real fear that the Japanese would never give up, Japanese eyewitness accounts of the tragedy in Hiroshima, diaries written on board Enola Gay, and the personal testimony of Colonel Paul Tibbets, the man who led the mission so secret not even his crew knew the enormity of what they were doing.

14 October 1947 and 4 January 1967. Compelled by a sense of patriotic duty and driven by incredible bravery, 20 years separate the determined efforts of two mens aim to become the fastest men on the planet.