Renowned swordsman Ye Gucheng (Jason Pai) suddenly challenges his compatriot Ximen Chuixue (Elliot Ngok) to a duel to the death on the eve of the Mid-Autumn Festival.

This unusual series of events spurs the intrigue of several martial artists including Lu Xiaofeng (Tony Liu), who summons his compatriots Hua Manlou (Sun Chien), Monk Honest (Walter Tso), Sikong Zhaixing (Lung Ting-sang), and Hermit Pine (Shum Lo) to uncover the true reason for the match.

They consult Guisun Daye, a mysterious and seemingly all-knowing hermit, and Lu is directed to two gamblers, Du Tongxuan (Yeung Chi-hing) and Li Yanbei (Cheng Miu).

Lu then narrowly escapes being assassinated by a mysterious elderly man in imperial robes, whom he later sees gifting Ye medicine for his sickly wife, Leng Qingqiu (Ching Li).

Ximen agrees to hand over the antidote and Lu realises he too does not know why Ye wishes to duel him and is also trying to uncover the truth (thus the real reason he postponed their match).

Lu then learns that Li Yanbei has relinquished his bet to Kuo Chingfeng (Ai Fei), the leader of the White Cloud sect and godchild of the chief imperial eunuch, Wang An (Tang Ching).

Kuo does not disclose any reason in taking up on Li’s bet, and Lu later witnesses him meet with the chief lama of the Holy Water Sect from Tibet.

When Kuo departs to talk in secrecy with a man called Gan Er Jiao (Lam Fai-wong), Lu recognizes him as the one who released Yan Renying’s horse.

Lu reluctantly believes Ye truly committed the murders but Hua Manlou contradicts this as the poison in his wound should have left him severely weakened and unable to move, let alone fight.

The truth of the plot is revealed: Wang An plans to use Ye to assassinate the current emperor and install the illegitimate heir to the throne, whereupon imperial China will be absorbed into a part of Tibet.

When the duel between Ximen and the fake Ye takes place, Hua Manlou notices Lu’s absence and upon hearing Kuo Chingfeng is nearby, suspects he may be involved.