In 1969, physically fit Taiwan native Lo Pao-tai (Ethan Juan) arrives in Kinmen as a new Republic of China Army conscript. He is selected by Sergeant Major Chang Yun-shan (Chen Jianbin) to be part of the 101st Amphibious Reconnaissance Battalion (also known as the Frogmen of the R.O.C. Army) for grueling training, where he underperforms. He helps Chang Yun-shan—an illiterate who twenty years ago was kidnapped by the R.O.C. Army from his Shandong village and forced to leave the mainland—and Chang in turn arranges for his transfer to work in the military brothel known as Unit 831.