The film opens with a dazzling display of two kung fu arts: Iron Armor, which renders a fighter nearly invulnerable, and Eagle Claw, touted as the deadliest technique. On patrol through a busy town, Ming General Chow watches a skilled fighter, Hu Lung, fend off a swarm of bandits with calm precision. Impressed, the general arranges for Minister Liu, the head of Royal Security, to meet him as a potential recruit and test his mettle.
During a courtyard spar with the minister, Hu Lung suddenly produces a knife and assassinates the minister before escaping over the wall. General Chow rushes to Liu’s aid, but the guards arrive and arrest him, taking him away as a suspect in the murder. En route to the court, a group of soldiers arrives with orders to kill Chow, but the highly skilled fighter turns the tables, defeats his captors, and makes a narrow escape.
Ming Minister of State Minister Cheng, a strict authoritarian and master of both the Iron Armor and Eagle Claw, responds by dispatching his most trusted enforcer, Shen Yu, to track down Chow and secure Chow’s return. Meanwhile, Chow continues his pursuit of Hu Lung, all while dodging the authorities who are bent on his capture. He finally locates Hu Lung, but Shen Yu intervenes, forcing a tense confrontation between Chow and the enforcer. Chow insists that Hu Lung is the real murderer, but Shen Yu remains unconvinced, and the clash ends with Chow slipping away once more.
The story expands to reveal Hu Lung’s backstory: the old man who confronts Chow and Shen Yu is Hu Lung’s former teacher, who had expelled Hu from their clan. Hu confesses that Minister Cheng, a former classmate of the old man, paid him to carry out the assassination. The old man confronts Cheng and sets a trap to kill him, using Hu as bait, but the trap fails and Cheng kills the old man while Hu escapes yet again.
Chow learns the Iron Finger technique from the old man’s grandson and granddaughter—an ability capable of defeating Cheng’s Iron Armor. But training is interrupted when Shen Yu and another enforcer sent by the Minister arrive to arrest Chow. Shen Yu doubts Chow’s guilt and gives him three days to locate Hu Lung and clear his name. Before Chow can reach Hu Lung, Hu is killed by Cheng, but Shen Yu discovers evidence on Hu’s body that ties the minister to the crime. That night, at an inn, multiple assassins attack Shen Yu, yet he is saved by an unknown ally who also leaves him a strange letter.
The next morning, Shen Yu confronts Cheng, who offers to enlist Shen Yu’s support, an offer Shen Yu rejects. With few choices left, Chow joins forces with the old man’s two grandchildren to confront Cheng’s henchmen. In the climactic showdown, Chow discovers Cheng’s weak spot: his ability to retract his testicles into his body for protection. Harnessing the Iron Finger technique and the combined efforts of Hong Kong’s unique fighters, Chow forces Cheng to reveal and then crush the vulnerable area, killing Cheng and vindicating Chow.
