1948年，东北全境解放，敌人的破坏活动也随之而来。治安处接到情报，一个叫李天民（吕班 饰）的敌特潜入本市，处长(方荧 饰) 和张队长（张平 饰）立即布置人员抓捕。在审讯中，李天民避重就轻，拒不交待实质问题。不久，在一个送牛奶的孩子所送牛奶的瓶塞上发现了端倪，他将空瓶交给了另一个特务周少梅（罗泰 饰）所有一切都被我侦察人员掌握，此时周少梅判断李天民可能出了问题，怕引火烧身，他把小孩杀掉灭囗。我侦察人员充分发动群众，给隐藏的敌人造成很大的心理压力，好多受蒙蔽的人员纷纷给公安人员提供破案线索。敌人终于沉不住气了，完全陷入了人民战争的天罗地网......

Factory workers in 1947 repair a bridge over Song Hua River so that Communist forces can use it.

Four students in Shanghai have recently finished university. All are unemployed. Xu contemplates suicide but his friend Zhao talks him out of it. Zhao lives in a shabby room with just a flimsy wall of planks separating him from the room behind. Miss Yang, in town to take a factory job, moves in behind. Her nails into the wall knock Zhao's photos down. The unseen neighbours start playing tit for tat... Zhao gets a job as proofreader at a newspaper. He sees that pretty girl on the tram to work every day. He doesn't know her, but it's Miss Yang... Zhao is assigned to cover labour conditions for the paper. He is sent to a factory, the one where Miss Yang works...