Ko Da-fu (Charlie Chin) is the leader of a five-man hit squad that only accepts contracts taken out on visitors, not native Hong Kong people. Having been in the business for many years, Ko's reaction time and reflexes are starting to slow, thus he barely escapes when attacked by a gang of punks on rollerskates. His four partners are not so lucky, as they are ambushed by the Wa-hing Triad in a parking garage.  The Wa-hing boys apparently seek to avenge a Japanese associate who was terminated by one of Ko's men. The Wa-hing bosses (including Kwan Hoi-shan, Lau Siu-ming, and Chan Shen) decide to spare Ko's life since he used to be one of their gang; but this is a decision they soon regret.

On the run, Ko returns to Sai Ying Pun, where he once worked as a coolie.  There, the severely injured Ko is nursed back to health by local girl Ton Ke-yee (Cecilia Yip). But he is far from safe, as the Wa-hing boys and a slovenly but determined Police Inspector Chung (veteran martial arts star Yueh Hua) close in.  The choice he makes in saving Yip is an odd one by our society's morals, and after so much time is probably the weakest point of the whole film.

A classic film of its time, and well above average compared to similar Hong Kong crime thrillers of its era, The Coolie Killer offers some terrific fight scenes and the story manages to provide a couple of surprises during the final scenes. There are some nice comic touches which enhance the rather brutal violence and Terry Tong, a talented director who never lived up to the potential displayed in earlier films, elevates several otherwise ordinary moments with style, such as when Ko is being chased by the roller-skating killers around the circular lobby of his apartment building, a scene which plays out like a deadly version of the roller derby game TV shows of that era.  Perhaps most surprising is that the soundtrack includes some early Tangerine Dream.