In Rome, Chen Ching-hua and her uncle Wang experience trouble with their restaurant from a mob boss who wants their property. When Chen refuses to sell, the mob boss sends gangsters to scare away customers. Appealing to an uncle in Hong Kong, Chen receives help in the form of Tang Lung, a martial artist. Disappointed, Chen asks how he can help her, but Tang confidently assures her that he is capable. At the restaurant, Tang learns that the staff have begun to learn karate, much to the annoyance of Quen, an employee who favors Chinese martial arts. Tang tells Quen that he should be open-minded and incorporate any moves that work. Before Tang can demonstrate his style to them, customers arrive, and the staff change clothes.
Before long, gangsters appear at the restaurant and chase off the customers while Tang is in the bathroom. Angered by Tang’s poor timing, the staff question his skill and the usefulness of his style. Later, the gangsters return to harass more customers. Before the staff can engage the gangsters, Wang asks all involved to take their fighting outside. The staff engage the thugs, only to be beaten. However, Tang single-handedly defeats the thugs, and the staff abandon their training to study under him. Wang warns them that the gangsters will now seek revenge and that this victory could make the situation worse. Tang vows to protect the restaurant. Chen and Tang grow closer, and she takes him on a tour of Rome, though Tang is unimpressed.
Ho, the mafia boss’s consigliere, returns with armed thugs and takes the restaurant staff hostage while they wait for Chen and Tang to return. Ho gives Tang a ticket back to Hong Kong; when his men escort Tang outside, Tang quickly disarms and overpowers them. When reinforcements from the restaurant arrive to subdue him, he defeats them using a pair of nunchaku. Tang warns Ho not to return, and the thugs leave the restaurant. The staff celebrate their victory, though Wang again urges them to focus more on business than fighting. Meanwhile, the mafia boss threatens to send an assassin to kill Tang unless he leaves by Chinese New Year, and Wang urges Chen to convince Tang to leave.
When Tang refuses to abandon the restaurant, the assassin targets him from a nearby rooftop. On edge from nearby fireworks, Chen and Tang survive the attempt, and Tang races off to confront the assassin, whom he tricks into wasting his ammunition. When he returns to the apartment, he finds Chen gone. Assuming that Ho has kidnapped her, Tang arrives at the mafia boss’ headquarters and leads the restaurant staff in a battle, which they win. Tang issues a final warning to the mafia boss, which Ho translates. The staff again celebrate, but a telegram for Tang cuts this short when they learn that he has been summoned back to Hong Kong. Tang assures them that he will not leave without seeing the situation resolved.
Ho hires two martial artists to challenge Tang, Japanese and American karate practitioners who initially refuse to work together. When the mafia boss indicates that money is no issue, Ho also recruits the American’s sensei, a world-class martial artist named Colt. Ho leads the restaurant staff to an isolated spot under the pretense of a truce, where the two hired martial artists attack them, and Ho lures Tang away to fight Colt at theColosseum. After they defeat the martial artists, Wang betrays and kills two of the staff, as he wants to sell the restaurant to the mafia boss and return to Hong Kong.
In a brutal fight, Tang injures and then disables Colt. When Colt refuses an offer of mercy, Tang kills him. The mob boss arrives at the original location as Tang and Ho return, and the boss kills both Ho and Wang. The police arrive and arrest him as he attempts to also kill Tang. As Tang leaves for Hong Kong, Quen tells Chen that Tang is a loner who will never settle down.