Ten-year-old Yang-zi steals her mother's diary to find out the truth about why her mother abandoned her.

In the early days of the founding of the People's Republic of China in 1949, New China was faced with "internal and external troubles". Since the outbreak of the Korean Civil War, the U.S. military has repeatedly provoked the border between China and North Korea, and civilians have been brutally bombed. In order to maintain the hard-won peace and long-term stability for generations, in October 1950, the Chinese People's Volunteers entered North Korea, and the "Resist US Aid Korea" war kicked off.

The movie focuses on the battle of Cheolwon, where the 63rd Army of the Chinese People's Volunteer Army (CPVA) was ordered to enter the battlefield of Cheolwon in May 1951, just after a month-long battle, to fight against four divisions of the United Nations Army (UNA). The volunteers fought with bloodshed and finally brought the enemy to the negotiation table.

A series of murders strikes the city of Fentun. The crimes mysteriously stop without the authorities having been able to find the perpetrator. Eight years later, a young police officer, close to one of the victims, decides to reopen the investigation.