Plot

During China's Tang dynasty the emperor has taken the princess of a neighboring province as wife. She has borne him two sons and raised his eldest. Now his control over his dominion is complete, including the royal family itself.

A Chinese emperor (Chow Yun-Fat) returns to his palace to discover his wife (Gong Li) is having an affair with her stepson, the Crown Prince (Jay Chou), who is himself actually in love with the Imperial doctor's daughter. In the lead up to the Chong Yang festival, an army of golden-plated warriors lay siege to the palace.

China, Later Tang Dynasty, 10th Century. On the eve of the Chong Yang Festival, golden flowers fill the Imperial Palace. The Emperor (Chow Yun Fat) returns unexpectedly with his second son, Prince Jai (Jay Chou). His pretext is to celebrate the holiday with his family, but given the chilled relations between the Emperor and the ailing Empress (Gong Li), this seems disingenuous. For many years, the Empress and Crown Prince Wan (Liu Ye), her stepson, have had an illicit liaison. Feeling trapped, Prince Wan dreams of escaping the palace with his secret love Chan (Li Man), the Imperial Doctor's daughter. Meanwhile, Prince Jai, the faithful son, grows worried over the Empress's health and her obsession with golden chrysanthemums. Could she be headed down an ominous path? The Emperor harbors equally clandestine plans; the Imperial Doctor (Ni Dahong) is the only one privy to his machinations. When the Emperor senses a looming threat, he relocates the doctor's family from the Palace to a remote area. While they are en route, mysterious assassins attack them. Chan and her mother, Jiang Shi (Chen Jin) are forced back to the palace. Their return sets off a tumultuous sequence of dark surprises. Amid the glamour and grandeur of the festival, ugly secrets are revealed. As the Imperial Family continues its elaborate charade in a palatial setting, thousands of golden armored warriors charge the palace. Who is behind this brutal rebellion? Where do Prince Jai's loyalties lie? Between love and desire, is there a final winner? Against a moonlit night, thousands of chrysanthemum blossoms are trampled as blood spills across the Imperial Palace.—Sony Pictures Classics

On the eve of the Double Ninth Festival, the Emperor (Chow Yun-fat) and the second of his three sons, Prince Jai (Jay Chou), return from their military campaign to Nanjing so they can celebrate the holiday with their family. However, the Empress Phoenix (Gong Li) has been in an affair with the first son, Crown Prince Wan (Liu Ye), who was born of the Emperor's previous wife. At the same time, Crown Prince Wan has been in an affair with Jiang Chan (Li Man), daughter of the Imperial Doctor, and is keen on rejecting the throne so that he may run away with her. The Emperor cancels the welcoming ceremony for Jai and instead meets him outside the city limits. He tells Jai to remember his past mistakes and to be happy with what he gives Jai. Jai is Phoenix's son from the Emperor. Prince Yu (Qin Junjie) is Wan's brother.

Prince Jai notices the declining health of his mother, and is confused by her sudden interest in chrysanthemums, the golden flowers. Imperial Doctor & his daughter Jiang Chan are knowingly involved in poisoning the Empress on the Emperor's command. At a family lunch, The Emperor forces Phoenix to drink the medicine that she discarded earlier in the day. Wan asks for permission to be sent to the front, while Yu wants permission to command the guards on the night of the chrysanthemum festival, but Emperor gives this command to Jai. In private, Wan asks the emperor to appoint Jai as the crown prince. The Empress hires a mysterious woman to discover the type of poison which she is suffering from (black fungus from Persia, fed 2 grams a day, which will make the Empress lose her mind), but the woman is captured by Crown Prince Wan and taken to the Emperor. As it happens, the woman is Jiang Shi (Chen Jin), the Imperial Doctor's wife, whom the Emperor imprisoned a while ago (after she ran off with the Imperial doctor. But Jiang Shi retorts that back then Emperor was a lowly captain and wanted to marry the daughter of the Emperor to gain the title himself. He killed off Jiang Shi's family and was close to murdering her as well) and who was believed dead, but somehow escaped. The Emperor decides to pardon her and to promote the Imperial Doctor to governor of Suzhou and orders him to leave the palace.

The Empress catches Wan having sex with Jiang Chan. The Empress explains to Jai that the tea she drinks has been poisoned for some time (for about 10 days) by the Emperor, but that she is planning a rebellion to overthrow him. Prince Jai agrees to be the leader of the rebellion. When Crown Prince Wan meets with Jiang Chan to say goodbye (outside the city), she informs him that the Empress has woven 10,000 scarves with golden flower Sigils. They are discovered by Jiang Shian, who is horrified, and orders Wan to leave (who is bewildered as nobody talks to him like that). Crown Prince Wan confronts the Empress, and when she admits to planning a rebellion, he is anguished, and tries to kill himself with a knife, but survives. The Emperor meets Wan and tells him that he knows that he has been intimate with the Empress, but he is kind to Wan. Wan tells him about the planned rebellion.

On the way to Suzhou, the Imperial Doctor's Jiang (Ni Dahong) household is betrayed and attacked by the Emperor's black assassins, resulting in his death. Jiang Shi and Jiang Chan run back to Nanjing (under protection from royal guard provided by the Empress) and confront the Emperor, who refuses to answer, whereupon the Empress explains to Jiang Chan that Jiang Shi was the Emperor's first wife and Crown Prince Wan's mother, meaning that Jiang Chan and Crown Prince Wan are half-brother and sister. Jiang Chan is horrified by this news and runs from the palace. Jiang Shi chases after her, whereupon both are murdered by more assassins. At this point, the third son, Prince Yu, suddenly murders Crown Prince Wan and reveals he has been aware of the corruption of both the Emperor and the Empress. Summoning a group of his own soldiers, Prince Yu demands the Emperor abdicate and offer him the throne. However, even more assassins descend from the ceiling, and they easily defeat Prince Yu's soldiers. The Emperor proceeds to whip Prince Yu to death using his belt.

Meanwhile, the outer square of the palace is assaulted by 10,000 soldiers wearing gold armor and gold flower Sigils, with Prince Jai in the lead. They overpower the assassins and proceed to the inner square of the palace, trampling upon the bed of golden flowers arranged for the ceremony. However, thousands of silver armored soldiers appear, being the reserve army of the Emperor, bearing shields, pikes, and bow-and-arrows, and they slaughter the golden soldiers down to the last man. Prince Jai rises from the sea of bodies and is taken captive. Behind him, the courtyard is cleaned with mechanical efficiency by a legion of servants, with bodies being removed, floors being scrubbed and laid with carpets, and pots of yellow flowers being replaced, making it seem as if the entire rebellion never even happened.

At midnight, the Double Ninth Festival begins as scheduled. At the table, the Emperor expresses disappointment with Prince Jai, saying that he was already planning to give Prince Jai the throne. Prince Jai says that he did not rebel to obtain the throne, but for his mother's sake. The Emperor responds by offering to pardon Prince Jai if he cooperates in the Empress's poisoning. Prince Jai refuses and kills himself, and as he does so, his blood spills into another cup of poisoned tea that has been brought to the Empress, turning the tea red. Horrified, the Empress slaps the tea away, and the liquid is shown to corrode the table's wood, along with the golden flower image engraved into the wood.