Silmi Island

In the late 1960s, tensions between the north and the south of the Korean peninsula were tense, and both sides launched crazy espionage and assassination operations. In January 1968, Kang Rencan (played by Xue Jingqiu) was sentenced to death for murder. Before execution, he was suddenly called to the detention room to discuss the conditions of alternative death penalty with special forces officers. He will be sent to the deserted island of Shiwei in the southwest to receive special military training. At the same time, another 30 dead prisoners also accepted the conditions of special forces officers and were recruited to Shiwei Island to perform special missions. After these 31 death row prisoners arrived at Silmi Island on a fishing boat, under the announcement of their superior, Lieutenant Choi Jae-hyun (played by Ahn Sung-ki), they formed the "684 Northern Troop" with the goal of assassinating North Korean leader Kim Il Sung, and immediately received a series of hellish physical and military training. However, three years later, due to changes in the national policy of the South Korean government, the plan for the "684 Northern Troops" was canceled, and the future of the 31 members was uncertain. They all feel betrayed by the country and can only try to save themselves...