A Fist Within Four Walls (Chinese: 城寨英雄; Cantonese Yale: Sìngjaaih Yīnghùng) is a 2016 Hong Kong martial arts action television drama produced by Jazz Boon and TVB.

[1] The plot revolves around Chor Au-kuen, a gifted martial arts novice who takes on the duty of protecting the walled city against evildoers.

The walled city was a largely ungoverned settlement at the time, with high rates of gambling, prostitution, and drug use, earning the name "Three Lawless Zone" (三不管; saam1 bat1 gun2).

In 1945, Bajiquan masters Duen Tung-tin and Chiu Mang-san form a brief alliance to protect the once-peaceful Kowloon Walled City from falling into the hands of ruthless gangs.

Fifteen years later, Chiu's now adult son Chor Au-kuen returns to the walled city to find his long-lost sister.

Concealing his true identity, he gets acquainted with Tiu Lan, the lady boss of a local hair salon, and finds a job as a water labourer so he can pay his rent.

Instead, Kuen takes up the mentorship of store owner Yuk Bo-fung, a retired kung fu master, and learns mixed styles of Muay Thai and Wing Chun.

Her son Lung Shing-fu, the right-hand man of Fellow Association leader Or Man-cheung, finds his loyalties divided.

When his father was accused of a crime and later killed, 10-year-old Kuen escaped the walled city to Macau to live with his great aunt.

[1] He gets acquainted with several martial artists within the city and takes up the mentorship of Yuk Bo-fung, a master in Muay Thai and Wing Chun.

Tiu Lan has a mysterious past, and has demonstrated on several occasions that she is an extremely skilled mixed martial artist, with a fondness for knives.

Known as Ngah Lo (牙佬; "Tooth Guy"), Kuen's occasional rival and the successor of the Duen Family Bajiquan.

When Fung was 10, his father was beaten to death by a mysterious assailant, and his family was forced to close down their Bajiquan kwoon due to the growing intimidation of triads.

A rough childhood turned him into a heartless, cruel, and a little twisted in the mind, but he remains extremely protective of his younger brother, Fung Ha-moon.

She is a retired Wing Chun and Muay Thai master from Mainland China, but moved to Thailand to start her family.

Fa Man is a powerful Bajiquan fighter, and was hired by Fung Chun-mei to cause unrest between Or Man-cheung and Fuk Sau-kam.

The honest owner of a put chai ko (缽仔糕) factory who helps the walled city citizens as much as possible, while smuggling drugs for Fuk Sau-kam to protect his employees.

On 15 April 2015, TVB and producer Jazz Boon announced the development of A Fist Within Four Walls after casting martial arts star and action choreographer, Philip Ng.

[3] The series would revolve around a group of martial artists living in the Kowloon Walled City, an ungoverned former enclave in Hong Kong.

The cast was finalised in July 2015 with the addition of Ruco Chan, Nancy Wu, Yuen Qiu, and Grace Wong.

On 26 July, a week before the drama's premiere, Hong Kong manhua author Yu Yee accused A Fist Within Four Walls of plagiarism, claiming that parts of the character design in Fung Chun-mei (portrayed by Carlo Ng) came from a character in his manhua City of Darkness, a story that also takes place in the Kowloon Walled City.

Producer Jazz Boon responded by saying that the characterisation of Fung Chun-mei is actually inspired by Dongfang Bubai, the famous villain in the popular wuxia novel The Smiling, Proud Wanderer by Jin Yong.

[17] Online critics praised the drama's humor, action-packed story and well-written characters[18][19] but criticised the predictable plot[20] and the overuse of slow motion shots during the fight scenes.

[15] Several critics noted the cultural elements of the drama, and interpreted them to be a social commentary on Hong Kong's current political situation.

Lam Tung-yin of HK01 said the last episode was ridden with clichés, corny twists, and that the final villain was given an anticlimactic and lazy ending.

"Viewers in millions" refers to the number of people, derived from TVB Jade ratings, in Hong Kong who watched the episode live.