A dying master of the Poison Clan is training his final student, his sixth. Fearing the skills he taught to his previous students are being used to evil ends, he sends this student, Yan Tieh (played by Chiang Sheng), on a mission: Trace his former students, assess their moral standing (dispatching them if necessary), and protect the master's old partner. His partner became rich through the clan and he fears the old students will seek to steal the fortune.
During the course of his journey, Yan Tieh meets all five students. Alternatively referred to by their number (the order in which they were trained) or by their animal style, each student was taught only 1 of the 5 poison styles. Yan Tieh, number 6, was taught all 5 styles, but he had only 3 years of training so his master tells him "You must join up with one of the five, or you will have no chance of defeating them."
Number 2 (played by Wei Pei) is the Snake. He has a two pronged attack. He has the snake's mouth on one hand whereby using precise finger control he attacks the pressure points mimicking the poisonous effect of a snake bite. On his other hand is the stinging tail. He fights extremely well on his back. He and Number 1 trained at the same time. Nevertheless all students wore masks to hid their identities from each other. His color is silver. His identity is a rich nobleman.
Number 3 (played by Sun Chien) is the Scorpion. This style is all about striking. Hard. His kicks are like the stinging tail and his fists are like the pincer. He trained alone with the master and never met Number 1 or Number 2. He remains in the shadows for most of the movie. His color is either black or purple.
Number 4 (played by Kuo Chui) is the Lizard. The oldest of the fighters, he studied at the same time as Number 5. Remember that they all wore masks so none of them know the identities of the others. The lizard is an agile and nimble style. He can climb walls and fight with extreme dexterity from them. His color is gold.
Number 5 (played by Lo Meng) is the Toad. The movie's description of this style must be quoted and certain people may remember the line appearing a Wu-Tang Clan song. "The toad style is immensely strong and immune to nearly any weapon. When it's properly used, it's almost invincible." He can bend metal. His color is green as shown in the open sequence. However, he wears a brown or black coat or goes bare-chested for most of the film.
This film provides examples of:
- Achilles' Heel: The Toad is superhumanly tough, but once his ears get smashed, he's powerless.
- Animal Theme Naming: All the main characters/former students, except for Number 6, are given an animal name based off their Kung Fu style that mimics the animal.
- Avenging the Villain: Snake for Centipede.
- Arrogant Kung-Fu Guy: Most of them.
- Beard of Evil: Number 1, aka Centipede, has this. It's even lampshaded by the witness. Number 4, aka Lizard, aka Constable He just has a Badass Beard.
- Big Bad Duumvirate: At first it seems like Number 1 is set up to be the main Big Bad, but throughout the film, the balance of power among the antagonists' alliance sways between the central antagonists.
- Boisterous Bruiser: Number 5, Brother Toad.
- Color-Coded for Your Convenience: The one of the primary antagonists wears red. His second in command wears silver.
- Devil in Plain Sight: Two of the Venoms are local constables, and one is a rich nobleman. Subverted, in that one of the constables is actually good.
- The Dog Bites Back: Brother Scorpion turns on Brother Snake in the final fight, which turns out to be a mistake...
- Hanging Judge: The local Judge
- Heel Realization: At the start of the third act, Snake takes a brief moment to lament to Scorpion that while he doesn't actually want the treasure since he's already rich, he keeps killing to keep himself out of trouble, and asks when will it end. Scorpion laughs it off, saying that once started, it will never end.
- He Knows Too Much: The informant and the witness are both killed.
- Hong Kong Dub
- Iron Maiden: The film features an iron maiden variant with the victim's head exposed. Snake uses this to defeat Toad's "iron skin" power, but it only takes after Scorpion and Snake smashes his ears and disables ability.
- Kangaroo Court: In the murder trial, the judge is desperate to get a conviction quickly, not solve the case. Listening to the poisonous whisperings of Snake, the trial devolves into this rather quickly, ending in the conviction of Toad and the acquittal of Centipede. This was after Centipede was initially identified as the murderer, and he was apprehended thanks in no small part to Toad.
- Karma Houdini: The judge does not get any punishment but one character does suggest it, only for another to say that his replacement could be worse.
- Lonely Rich Kid: Brother Snake, born into a rich family but entered the Poison clan just to master style of kung fu and is only started after the treasure because of loyalty to Centipede.
- Martial Arts Movie: Obviously.
- Nigh Invulnerable: The Toad can shrug off iron spikes and bend sheet metal with his bare fists. Just don't hit his weak point...
- Obfuscating Stupidity: Yan Tieh spends the bulk of the film pretending to be just a begger to go under cover.
- Old Master: It is implied that the head of Five Venoms House is this, but partially subverted due to the fact that he is dying at the beginning of the movie.
- A Pupil of Mine Until He Turned to Evil: Head of Five Venoms House fears this to be the case for all his students except Number 6.
- Rapid-Fire Fisticuffs: Centipede style's specialty.
- Red Herring: The Scorpion is not the judge.
- Red Oni, Blue Oni: Number 1 (red) and Number 2 (blue) along with a similar relationship between Number 4 (blue) and Number 5 (red).
- The Red Mage: Yan Tieh, the last/sixth disciple, is essentially the kung fu version of this, knowing traces of all the techniques but not being an expert in any to stand against the others alone.
- Sacrificial Lion: Number 5.
- Shirtless Scene: Everyone wears open-fronted shirts, but Lizard is shirtless during the final battle.
- The Stool Pigeon: Wong Fa
- Sixth Ranger: The Hero is this.
- Too Awesome to Use: Non-item example but Brother Toad is especially frustrated that he has to pretend to just be a random strong man and keep his true skills in secret. It's due to being one of the Venoms that a signature move set is such a revealing calling card.
- Torture Always Works: To both Centipede and Toad during the murder trial. Neither of the tough guys actually break under torture—but they're both really anxious not to undergo it again.
- Totally Radical: According to at least one version of the English subtitles, Snake's full title is "Snake Spirit Dude". This is only referred to once, then never mentioned again.
- Wall Crawl: Lizard style specialty