Mad Detective (Chinese: 神探) is a 2007 Hong Kong action film[2][1] produced and directed by Johnnie To and Wai Ka-Fai.

Later, Inspector Ho Ka-On (Andy On) is investigating the case of Wong Kwok-Chu (Lee Kwok-Lun), a colleague who went missing when he and his partner, Ko Chi-Wai (Lam Ka-Tung), were in pursuit of a suspect.

"[6] Ty Burr of The Boston Globe wrote that Mad Detective "is equal parts gonzo inspiration and overwrought indecision", and nicknamed the film "'The Lunatic From Kowloon.

'"[7] Upon its release in Hong Kong, Mad Detective faced stiff competition with American films 30 Days of Night and The Heartbreak Kid.

The film was considered a great success by its Hong Kong distributor China Star, which took it out on a midsized 30 prints.

[8] Finally, it grossed over HK$10.67 million, which is considered to be a good result for a film that received a Category III rating in Hong Kong.

[11] Eureka Entertainment acquired the distribution rights for the United Kingdom, opening theatrically on 18 July 2008 at the Institute of Contemporary Arts (ICA) London and nationwide after that, with DVD and Blu-ray Disc editions released on 20 October 2008 as part of their Masters of Cinema series.