Plot according to Wiki http://en.wikipedia.org/wiki/The_Assass
The film is set in China between the late 190s and 200s towards the end of the Han Dynasty. Cao Cao had defeated Lü Bu and many other rival warlords to gain supremacy in northern China. In 216, Cao Cao was granted the title of a vassal king - King of Wei - by Emperor Xian. He then had the Bronze Sparrow Platform constructed as a display of power.
Lingju is the orphaned daughter of Lü Bu and Diaochan, and she, like many other orphaned children of Cao Cao's enemies, had been recruited in her childhood by Cao Cao's rivals to be trained as assassins to kill Cao Cao. She met Mu Shun, a castrated man, and fell in love with him. Lingju and Mu Shun both eventually found their way into the palace: Lingju became one of Cao Cao's mistresses while Mu Shun became a eunuch in the palace.
Throughout the film, there were two major attempts on Cao Cao's life. The first was masterminded by Empress Fu Shou and her father Fu Wan. This plan failed and Cao Cao had the conspirators (including the empress) executed in front of Emperor Xian. The second was a revolt led by the imperial physician Ji Ben and his supporters, but the rebellion was swiftly crushed. There is a brief scene showing that Cao Cao suspects that his son Cao Pi is involved in the assassination plots.
Mu Shun failed in his attempt to kill Cao Cao, who revealed that he knew all along that Lingju was planning to assassinate him. Cao Cao promises to spare Lingju's life, and in return, Mu Shun disguised himself as Cao Cao and rode out of the city, only to be killed by Ji Ben's followers. Lingju later committed suicide to join Mu Shun.