Two detectives who are up to their necks in trouble and in each other's face, as they try to shut down a drug-trafficking scheme that could be connected with international ties to organized crime. But in the midst of their investigation, innocent immigrant dock worker Luk Wan-Ting gets caught up in the mix when he witnesses the murder of an intelligence operative and is framed for the crime.
In the Line of Duty, sometimes referred to as the Yes Madam series, is a series of girls with guns feature films produced by Hong Kong movie studio D & B Films which star, in the first two, Michelle Yeoh, and, in subsequent installments, Cynthia Khan as a Royal Hong Kong Police Force officer who combines the use of firearms with kickboxing. The film Royal Warriors would be exported with the title In the Line of Duty and, due to its success, the film Yes Madam!, released one year prior, was retitled In the Line of Duty II: The Police Assassins as an export. Due to the overwhelming financial achievement of the films under the In the Line of Duty titles, D & B would start utilizing the In the Line of Duty title in their native Hong Kong market, with the third film being the first to originally use the In the Line of Duty name, which in turn would be retroactively applied to the two Michelle Yeoh vehicles. This would continue with the fourth entry before the series would revert to using individual unique titles.
