Set in the 1950s, the story follows Chor Au-kuen, a young man who returns to the notorious Kowloon Walled City—a lawless enclave in Hong Kong—to search for his missing sister and uncover the truth behind his father's death. Having suppressed his martial arts training for years, he is forced to break his vow of non-violence to protect the residents from the corrupt gangs and ruthless crime syndicates that control the area. As he navigates the treacherous underworld, he forms an unlikely alliance with Tuen Ying-fung, a mysterious dentist with a hidden past, and the spirited hairdresser Tiu Lan. Together, they fight to restore order and justice to the Walled City, facing off against powerful martial arts masters and uncovering a deep-seated conspiracy that threatens the very foundation of their community.