The story is set in the Jin State during the Spring and Autumn Period, the vicious minister Tu Angu can not get along with the loyal minister Zhao Dun. He devises a scheme and causes the King of Jin to kill the whole clan of Zhao's family of a total of 300 people.

Zhao's daughter-in-law, Princess Zhuang Ji, who is excluded from the massacre, has given birth to a child. Failing to beg humble the doctor Cheng Ying to protect her son, the princess commits suicide. Cheng Ying is deeply moved and finally promises to save the Zhao lineage. Tu learns that the orphan has been out of the palace. He orders to kill all the babies in the state within three days. After a discussion with Gongsun Chujiu, a loyal but elder minister of the Jin State, Cheng decides to sacrifice his own son and Gongsun sacrifices himself to save the orphan and other babies. Then Tu takes the orphan as his adopted son. Cheng does not tell anyone about the truth and suffers the misunderstanding of disloyalty for 18 years. After the orphan has grown up, Cheng tells him the truth and the orphan assassinates Tu successfully. Cheng Ying has kept his promise to the princess in the end.