The story happened around 8th century B.C. – 5th century B.C., which was the Spring and Autumn period in China's history. At that time, several states co-existed. Among them, there was one state called Jin. In the Jin state, there were two senior officials. One was called Zhao Dun, a loyal official to Jin. The other was Tu Angu, a military leader. The two did not get along with each other.
Tu used many stratagems to kill Zhao. Finally the Jin Emperor fell into his trap. He believed that Zhao was not loyal to him. So he ordered to kill Zhao's family as well as his servants, except one person, who was Zhao's daughter-in-law, Zhuang Ji. Zhuang survived because she was the princess.
At that time, Zhuang was pregnant. She later gave birth to a son. She named him the orphan of Zhao's family, hoping that the son could revenge for the Zhao family when growing up.
Knowing that the Zhao family had a son, Tu wanted to kill it.
A person wanted to save the infant. He was a friend of Zhao's, Cheng Ying, a doctor. In order to save the infant, Cheng pretended to treat for the princess with a medical kit. He put the infant into the kit and wanted to take it out of the palace. But the palace guard searched out the infant when passing the entrance. The guard sympathized for Cheng Ying and the infant. He let them go and then killed himself.
When Tu learned that the infant escaped, he ordered people to search it out, otherwise he would kill all the infants in the state.
Hearing this story, Cheng Ying began to discuss the issue with Gong Sun, a friend of Zhao. Cheng Ying had a child, which was of the same age as Zhao's child. Cheng Ying gave his child to Gong Sun. Then he went to tell Tu that Gong Sun kept the child of Zhao's family. Hearing this, Tu killed Gong Sun and the infant.
Tu was very glad. He thought that the infant from Zhao's family had been killed. He himself didn't have any child. So he regarded Cheng Ying's son (which was the actual son of Zhao's family) to be his adopted son and taught him martial arts. People in Jin state thought that Cheng Ying was a whistle blower who helped killed the infant from Zhao's family. They all blamed him. But Cheng Ying didn't explain. He brought up the child.
Fifteen years later, another official from Jin, Wei Jiang, had come from border. Hearing about the whole story, Wei Jiang was very angry. He beat Cheng Ying heavily.
Cheng Ying didn't say a word. On the contrary, he thought that if Wei Jiang beat him, it meant that he also hated treacherous court officials and could help the infant to revenge. Knowing for sure that Wei Jiang could help, he told him the true story. Wei Jiang was moved and promised to help the orphan.
Returning home, Cheng Ying told the orphan what happened by drawing pictures. The orphan knew about the story and promised to take revenge.