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 men Ah Hao (played by Liu Qingyun) and Ah Lek (played by Wu Zhenyu) inadvertently got mixed up in this atmosphere of turmoil and became enraptured by it, leading them into a life of indulgence. They partnered up to gamble on horse races and swindled money, which prompted a vengeful bookie to hunt them down. Fortunately, they were saved by Fat Bao, the big boss of the Walled City, and their fates began to change. Ah Hao apprenticed under Fat Bao and fell in love with his sister-in-law, the bold Ying (played by Peng Dan), becoming daring and brave; meanwhile, Ah Lek became a police officer and married a girl named Fei Fei (played by Zhu Yin), with whom Ah Hao had a past. To provide his vain wife a comfortable life, he chose the path of corruption and downfall. Two good brothers, each in their respective worlds of right and wrong, strove together to carve out a kingdom of their own...