Bao Si was the favorite of King You, last emperor of the Western Chou dynasty. She was given to the king as a peace offering by a tribal chieftain. The emperor was used to sycophantic concubines, vying for his favors. Therefore, he was intrigued by Bao Si's cold look of indifference, and made it his mission to elicit a smile from this ice maiden. He went as far as to dethrone the empress, mother of the crown prince, and put Bao Si in her place, but to no avail.

In the capital was a beacon, to be lit in the event of an enemy attack. One night, the emperor, in an attempt to amuse his favorite, ordered that the beacon be lit. The dukes and marquises gathered up their armies and rushed to the capital to defend their country. The people inside the capital were safe, but those living outside were thrown into mass confusion. When Bao Si saw this, she was delighted, and smiled. Much pleased, the emperor told everyone to go home, that he had only wanted to make Bao Si smile. From that day onwards, the beacon would be lit from time to time, with the same outcome. After a while, the dukes and marquises grew tired of being ridiculed, and refused to respond to the emperor's summons.

Not long afterwards, the father of the deposed empress, in collusion with a western minority tribe, invaded the capital. The emperor raised the war cry, but no one came to save him. He was forced to flee the city with Bao Si, only to be captured and put to death, bringing about the end of the Western Chou dynasty.