Based on the true story that really happened after World War II
This thriller is actually a spy movie that is based on the struggles between the communist undercover agents and the nationalist government's attempt to crackdown in Yun-Nan Province, in southwestern China. Although what was told in the movie was mostly true, the story was not complete:
What those undercover agents did not expect was the political movement in the post-revolutionary China, which put them in jail again in political persecutions during the Cultural Revolution, except this time it was the communist jail on their own side, and many perished. The story would be complete if there was a sequel made about the life after the revolution for these undercover agents.