This documentary introduces Dr Akemi Kirino, a Japanese scientist who invented a method of time travel that harnesses Bohm-Kirino particles to allow a witness to view historical events. The nature of these particles means that any given event can be viewed only once, and never again. Dr Kirino's husband, Dr Evan Wei, a Chinese-American historian, becomes obsessed with atrocities committed by the Japanese during World War II: a series of horrific human experiments that took place at a facility called Unit 731. He uses the Bohm-Kirino method to send relatives of the victims of those atrocities back in time to bear witness to these events in an effort to not only make this event better-known, but to seek an apology for survivors and descendents from the Japanese government. One of the witnesses he sends back uses the opportunity to find out what happened to her aunt, who was raped and deliberately infected with disease in Unit 731. The documentary also interviews one of the surviving doctors who carried out the experiments and who is now filled with shame and regret. The time machine and the focus on Japanese atrocities creates a great deal of backlash, both from uninvolved everyday people, who believe the past should be left in the past, and from the governments of China and Japan, who initially argue over who has the visiting rights to that era of the past, and later argue for disallowing visits to the past altogether. Over the years, these battles take their toll on both Dr Kirino and Dr Wei, as well as the countries involved. China and Japan reach the brink of war over the issue, and at last the United States steps in and shuts down the machine, outlawing its further use. Eventually, Wei commits suicide in despair. The documentary ends with Kirino's quiet admission that there was one secret she kept from Wei all her life: her beloved grandfather was a surgeon at Unit 731, and Wei personally used the machine to go back and witness him writing a loving letter to his family immediately before performing a dissection on a fresh brain. Wei was never able to reconcile her empathy for her grandfather with the knowledge of what he was. She concludes that allowing the truth to be told is all that matters.