Xu Xi (Jet Li) was originally a cold-blooded assassin in the mysterious killer organization Unit 701. Not wanting to be an instrument of murder anymore, he escaped the organization and came to Hong Kong, where he transformed into an ordinary library clerk. There, he met the police officer, Sir Shi, and they became friends. However, Unit 701 suddenly appeared in Hong Kong to pursue a gang leader, leaving Sir Shi and the police helpless. Seeing his friend in danger, Xu Xi stepped forward and became the Black Knight. The Black Knight infuriated the head of Unit 701, Xiong Ju (Long Gang), who then sent Xu Xi's ex-lover, Ruo Lan, to persuade the Black Knight to surrender. Xu Xi resolutely refused, resulting in the deaths of all his library colleagues except Tracy (Miriam Yeung). To protect Tracy, Xu Xi, as the Black Knight, took a tough stance to take her away, but Tracy, unaware that the Black Knight was her beloved Xu Xi, refused. During the confrontation with Xiong Ju and his men, Xu Xi gradually found the emotions he desired through Tracy.
