In Hong Kong, a Mr Braithwaite attends a sparring match of martial artists. Among them is a man named Lee who fights an opponent considerably larger than him. Lee himself is exceptionally skilled, forcing his opponent (Sammo Kam-Bo Hung) to yield. At the end of the match, several of the monks present raise their hands creating an obstacle that Mr Lee flips himself over easily, earning their applause.
Braithwaite meets later with Lee. Before Lee talks to Braithwaite, he gives a short lesson in harmony and control to a young male student of his, teaching the boy not to attack with anger or exposition. Lee also teaches the boy how to bow properly to earn the respect of an opponent. Braithwaite reveals his purpose for the meeting: Lee has received an invitation to a large martial arts tournament on a private island run by a reclusive man named Han. Han is suspected of doing business in prostitution and heroin, however no solid evidence can be found linking Han to any nefarious dealings. Braithwaite wants Lee to attend the tournament and act as a spy. Lee is slightly reluctant, having not wanted to attend the tournament, however he agrees.
Before Lee leaves for Han's island, he visits the Old Man of his Shaolin temple, who tells Lee about the day his sister was killed. Many of Han's thugs had come to the mainland and had attacked Su Lin. Though she skillfully and bravely fought them off, she was cornered in an old warehouse. Rather than be beaten and raped, she killed herself with a shard of glass. One of the men who led the attack, Oharra, Han's right-hand man, witnesses her suicide. The Old Man bids Lee to obtain revenge not only for his sister but for the honor of Shaolin.
Around the time that Lee is ready to board Han's sampan, two other men arrive. Roper, a fancy playboy of sorts, who totes a lot of baggage, has come to the Orient to hide out from the mob, to whom he owes money. In his last meeting with some mob thugs, Roper fought his way out of having his leg broken to repay his debt. The second man is Williams, a black man who was harassed and attacked by the police right after meeting with his sensei in the United States. When he was a attacked, Williams fought back, besting the two cops and escaping in their cruiser.
On the boat to Han's island, Lee and Roper both bet on a praying mantis match. Roper favors the larger of the two insects while Lee favors the smaller. Lee wins a handful of cash on the match. While Lee takes in the breeze from the harbor, an aggressive invitee named Parsons tries to antagonize him after tripping a boy carrying a load of fruit. He asks Lee about his fighting style; Lee answers it is "the art of fighting without fighting". Parsons scoffs, trying draw Lee into a match. Lee suggests that they take a small dinghy to a nearby island and match on the beach. When Parsons eagerly climbs down to the boat, Lee releases it from the sampan and lets it drift out behind, holding onto the rope and ordering Parsons not to pull himself in or he'll set him adrift on the ocean. Lee then hands the rope to the crewmembers, who are greatly amused.
On the island, the passengers see hundreds of other martial artists practicing on giant courts. That night, everyone attends a lavish feast. Han arrives, bidding welcome to his guests, praising them for their skill and thanking them for attending. He has several women with him who act as his elite personal guard. He tosses several pieces of fruit in the air while the women hit them with small darts, thrown with pinpoint accuracy. Lee catches one of them. After dinner, Han's hostess, Tania, brings young women to Roper and Williams -- Roper requests to spend the night with Tania herself. The woman Williams is with warns him not to step outside his room when Williams wants to get some fresh air.
When Tania visits Lee, he requests the young woman who threw the dart in the apple he'd caught at the banquet. Lee meets with the dart thrower, Mei Ling, who is actually a spy sent by Braithwaite prior to recruiting Lee. She tells him that she's found out very little about Han's illegal activities except that many young women who come to the island disappear. Lee later sneaks out of his room. Evading Han's guards, he finds a hidden trapdoor that leads to several underground chambers where Han has been cooking heroin. He subdues a few of Han's guards and is forced to retreat when the possibility of being discovered becomes too great. As he sneaks back to his room, Williams spots Lee climbing a nearby wall.
The next morning, Han attends the 1st few rounds of his tournament. He finds that Roper and Williams fight exceptionally well. Roper lays a few bets on Williams that pay off and has Williams lay down more bets. The two win a substantial amount of cash. Han appears and announces that one of his guests had been outside of their room after curfew and that some of his guards were attacked. He has his greatest fighter, Bolo, kill them all as punishment. Han later sends a message to Williams to meet him in his quarters. Roper is suspicious and tells Williams to watch his back.
In his meeting with his host, Williams is praised by Han for his abilities, though they are unorthodox. Han mentions that Williams fights more for glory than harmony but Williams shrugs off Han's opinion, saying he fights to look good. Han then accuses him of attacking his guards the previous night. Williams is immediately angered, demanding that he be allowed to leave the island. Han refuses and a couple of his thugs attack Williams, who defeats them easily. Han himself takes up a combat stance and the two fight around the close quarters of Han's office. When Williams tries to kick Han in the hand, he inexplicably injures his foot. Han takes advantage and finally beats Williams down, killing him with a single blow. He removes the glove from his left hand, revealing that it's made of solid bronze.
Back at the tournament, Roper beats a few opponents. Lee is called up to fight Oharra, one of Han's champions. With the memory of his dead sister to guide him, Lee lands several lightning-fast hits on Oharra. Oharra suddenly grabs one of Lee's feet with Han barking at him to let Lee go. Lee counterattacks with a vicious backflip kick to Oharra's chin that knocks him back. To finish him, Lee delivers a ferocious kick to Oharra's chest, knocking him into a few chairs and some of the spectators. Enraged, Oharra grabs two bottles, breaking them and brandishing the necks as weapons. Lee knocks the bottles from Oharra's hands and kicks him to the ground. Lee then lands a fatal blow to Oharra's throat. Han is flustered, telling the crowd that he has been disgraced by his champion and he leaves the court silently.
Han later meets with Roper, showing him his extravagant home. One room is filled with glass display cases and Eastern weapons. In one case are the bones of a human hand. Han cheerfully says the severed hand is a "souvenir". He takes Roper into a room with a guillotine, placing own cat under the blade. He tells Roper that real loyalty is being able to kill at request but Roper refuses to pull the release rope that would kill the cat. Han pulls the rope, which activates a platform that lowers them into the lower levels of Han's house. Down there Roper sees Han's heroin lab and the prostitutes and prisoners he holds. Most of the women have vacant looks, as if drugged. Han makes Roper a generous offer to join his operation but Roper refuses when Han shows him the body of Williams, hanging over a deep pool. Roper is visibly upset at the sight of his dead friend and Han has the body dropped into the pool. Roper is taken prisoner.
Needing to investigate further and to find a radio to get a message out to Braithwaite, Lee infiltrates the lower level again that night, picking up a cobra placed at the trapdoor to scare off any snoopers. Lee finds his way to the radio room, using the cobra to force the radio operators out. He gets his message out by telegraph. When he's discovered by Han's guards, he battles them, beating them with his fighting ability and their own weapons. After dispatching the last group, he rushes into another chamber but is trapped by closing metal doors. Above him, Han tells him that his fight with his guards was "extraordinary" and that he was planning to recruit him. Lee, however, has no desire and allows himself to be taken prisoner.
The next morning on the tournament courts, Han orders Lee and Roper to be pitted against each other but they both refuse to fight. Han menacingly says he'll find opponents for them to fight, starting with pitting Bolo against Roper. Bolo carries the fight to his advantage for a few minutes until Roper battles back and lands a hard kick to Bolo's crotch, taking all the fight out of him. Infuriated, Han orders his men to attack both Roper and Lee. They find themselves easily defeated. Lee moves on Han, who takes off his fake fist and replaces it with a clawed appendage. Lee battles him, receiving a few slashes but is able to disarm Han when the drug lord has his claw stuck on a table. Meanwhile, Mei Ling frees all of Han's prisoners, directing them out to the tournament courts where they engage Han's men.
Han runs off to his house with Lee right behind. In his trophy room, he takes an attachment for his wrist comprised of several sharp blades. The two square off - Han is able to slash Lee several times and wields a spear from his arsenal, however Lee is able to beat him back, forcing him to retreat behind a hidden door his spear becomes stuck in. Lee enters the room, finding it that it's entirely walled with mirrors. He moves slowly and deliberately, watching for Han. Han strikes a Lee a few times but Lee is finally able to work out an effective strategy: he begins breaking the mirrors around him, eliminating Han's advantage. He finally finds Han and gives him a vicious kick to the chest, impaling him on the spear he tried to use against Lee.
Roper sits on the tournament court exhausted after the battle with Han's men. He glances to the side and sees that Tania is dead. Lee arrives back at the court and they exchange a parting glance. The final shot of the movie is of Han's claw stuck in the table.