Set in the Song dynasty, the film opens with the upright Bao Zheng [Ching Miao] passing judgment on Pang Yu for embezzlement and ordering his execution. Enraged, the grand tutor Pang Ji [Tien Shun] schemes vengeance and sends assassins to avenge his son's death. A chivalrous officer, Zhan Zhao, the “Southern Hero” [Chang Yi], steps in to rescue Bao Zheng, and the emperor [Chin Feng] bestows upon him the prestigious title King Cat. This audacious honor sparks fierce jealousy in Bai Yutang [Kiu Chong], the “Brocade-Coated Rat”, who travels to Kaifeng, the capital, to challenge Zhan Zhao.
Bai is soon joined by his three elder sworn brothers — Han Zhang [Ku Wen-Chung], Xu Qing [Huang Tsung-Hsun], and Jiang Ping [Ngai Ping-Ngo] — and together they seize a treasure from the imperial palace, confident that Bao Zheng will send Zhan to retrieve it. On their way home, Bai’s companion is Ding Yuehua [Pat Ting Hung], the “Nine-Tailed Phoenix”, who confronts them and accuses them of raping and killing three imperial maids whose bodies are found soon after the theft. Infuriated by her lack of trust, Bai confesses, and Ding ends their relationship. The real mastermind, however, is Hua Chong [Lo Lieh], the “Flowery Butterfly”, who has been entangled with the treacherous grand tutor and his daughter, Consort Pang [Helen Ma Hoi-Lun], as well as a number of Taoist priests in a plot to overthrow the dynasty. Hua attempts to assault Ding, but Zhan intervenes and stops him.
Ding Yuehua then alerts Zhan Zhao to Bai’s guilt, and Zhan makes for the island where Lu Fang [Yang Chi-Ching] and his four sworn brothers hold Bai under watch, hoping to trap him. Ding Yuehua and his two brothers Ding Zhaolan and Ding Zhaohui arrive later, and Zhan narrowly escapes a trap hidden beneath a fish pond. In a crucial turn, Zhan learns that Bai was not the rapist, while Jiang Ping overhears Hua plotting to rape Princess Yong’an [Carrie Ku Mei] during her monastery visit. The heroes and their allies rush to the monastery, only to find it teeming with rebellious priests. With Bao Zheng’s army at their side, they subdue the rebels and ultimately kill Hua Chong, restoring a precarious order to the realm. The Five Rats return the treasure to the crown, and Zhan Zhao’s path crosses once more with Ding Yuehua, as the two begin a fragile, budding romance amid the lingering shadows of intrigue and loyalty.
