The three brothers in the Intelligence Department's eavesdropping team are like brothers. Liang Junyi (played by Liu Qingyun) is upright but cowardly, and he is indecisive in his personal emotional issues; Yang Zhen (played by Louis Koo) is in a difficult family situation. Not only does he have to deal with the sudden situation of his son who suffers from leukemia, but he is also terminally ill and will not live long; Lin Yixiang (played by Daniel Wu) is young and ambitious, and now he has "married into a wealthy family" and his future is limitless. The three brothers started to investigate the suspected insider trading case of the listed company "Fenghua International". They worked together and excellently completed the work of arranging various eavesdropping and monitoring equipment. During the continued monitoring process, they accidentally obtained a piece of intelligence. Under the temptation of huge profits, the three of them became greedy and made a fortune in the turbulent stock market. Afterwards, the three of them were afraid that the matter would be exposed, so they used their positions to destroy the evidence. Just when the three thought that the matter had settled, they never thought that the storm would rise again. An unexpected black hand attacked them, and the three of them fell into a robbery, were killed one after another, and finally ended tragically. "Three big men" challenge their limits, and two major teams ("Infernal Affairs" and "The Disciples") work together to create a deeply tragic story.