In the 1930s, Japan established Unit 731 in northeastern China. It was a notorious branch of the Imperial Japanese Army that carried out lethal experiments on thousands of prisoners. Before Japan surrendered in 1945, Unit 731 blew up its laboratories and prisons to destroy any evidence before leaving China. Hideo Shimizu was in charge of the operation and was ordered to keep it strictly secret. More than 70 years later, the aging Shimizu decided to break his silence and apologize to the Chinese people for Unit 731 and the crimes it committed.