Lin Xi, a gang member who hangs around the docks, is forced to get involved in the intelligence war between the Military Control Commission and the Japanese invaders because of a key. As a result, he and his good brother Li Yunfei get to know the progressive female student Su Nan and the upright and principled Military Control Commission agent Zhou Yingqun. The truth behind the key peels off layer by layer, and gang disputes and family and country chaos follow. In the dispute, Lin Xi, Zhou Yingqun and Li Yunfei experienced life and death and became brothers; Lin Xi fell in love with Su Nan and yearned for the belief in communism. Seven years later, the three brothers who were scattered all over the world reunited in Jinzhou. When they met again, their status was very different. The three of them had their own goals and fought for the camps they represented on the intelligence battlefield. New hatreds and old grudges, contradictory ideals, in the intelligence dispute and the rain of bullets, the three brothers calmly accepted their respective destinies, let go of their choices, reconciled with each other, and cracked the enemy's conspiracy with blood and flesh, extreme love and hate, and supreme ideals, and adhered to their ideals and beliefs in their hearts.