“In the Line of Duty IV” (1989) is a Hong Kong action film directed by Yuen Woo-ping, featuring Cynthia Khan as Inspector Yeung Lai-ching and Donnie Yen as Officer Donnie Yan. The narrative follows Yeung and Yan as they collaborate to protect a dockworker, Luk Wan-ting (portrayed by Yuen Yat-chor), who inadvertently becomes a key witness after being entangled in a drug smuggling operation.
The film opens with a failed drug bust in Seattle, leading to the death of a police officer and implicating Luk Wan-ting, who flees to Hong Kong. Yeung and Yan, both dedicated law enforcement officers, are assigned to track down Luk, believing he holds crucial information about the drug syndicate.
As the investigation unfolds, Yeung and Yan uncover a complex web of corruption involving both American and Hong Kong officials. Their pursuit of justice is fraught with intense martial arts confrontations, including a notable fight atop a speeding ambulance, showcasing the film’s high-octane action sequences.
The climax reveals the depth of the conspiracy, with Yeung and Yan confronting the true masterminds behind the drug operation. Their relentless pursuit not only exonerates Luk but also brings the corrupt officials to justice, highlighting themes of integrity and perseverance within the law enforcement community.