Undercover police officer Yu Chau (Nick Cheung) has successfully apprehended many criminals in the city of full of evil.

Because a child abduction case, Yu's identity is starting to be brought to light, attracting the hunt from criminal groups.

[3][4] The film's first teaser trailer was released on 11 March 2017 which was also presented at the 2017 Hong Kong FILMART.

[citation needed] The Trough was a box-office bomb, grossing only US$6,061,514 worldwide against a budget of US$22 million.

[2] In Hong Kong, the film grossed a total of HK$4,716,276 during its theatrical run from 3 May to 6 June 2018.