Lei Li lost his right-arm in a sword duel with the master of a martial arts school, long ago. Now, he is able to defend himself well with just his left arm, and kung fu techniques. That he proves with just the help of his friend Chung-Chieng, when he crosses his path with a beautiful girl in need, Pao Chiao. Even against impossible odds, he will prove a great warrior.

A dying teacher instructs his final student to check on the activities of five former pupils, each of whom he taught a unique and special style of kung-fu to: The Centipede, Snake, Scorpion, Lizard, and Toad (hence the title). His final student, who knows a little of each style must team up with one of the other good students to destroy the evil ones if there are any. Greed and treachery ensue as the student discovers that some of the students are indeed evil. But which one can he trust enough to team up with?

The anti-Ching patriots, under the guidance of Ho Kuang-han, have secretly set up their base in Canton, disguised as school masters. During a brutal Manchu attack, Lui manages to escape and devotes himself to learning the martial arts in order to seek revenge. In a short period of time he masters the deadly use of his fists, feet and palms, along with such weapons as swords, sticks, and lances. With his learning complete, he takes on the Manchus.