In the late 1950s and early 1960s, Hong Kong was rife with police and gangster collusion, creating a chaotic and fearful environment. Amongst this, Kowloon Walled City stood out as a notorious place where gangs thrived and sent shivers down people's spines. The aimless young man Ah Hao (played by Liu Qingyun) and Ah Lok (played by Wu Zhenyu) inadvertently got mixed up in this atmosphere of turmoil and became enraptured by it, leading them into a world of gambling and deceit. They found themselves pursued by the debt collectors, but their lives were saved by the city's big boss, Fat Bao. From that moment on, their fates took a turn. Ah Hao became Fat Bao's protégé and fell in love with Fat Bao's bold sister-in-law, Ying (played by Peng Dan), becoming braver and more charismatic as a result; meanwhile, Ah Lok became a police officer and married a girl named Fei Fei (played by Zhu Yin), who had once been involved with Ah Hao. To provide a luxurious life for his vain wife, he chose to succumb to corruption. The two brothers, standing on opposite sides of the law, worked together to carve out their own territory in this chaotic world...