During the Warring States period, there was a man named Nie Zheng from the state of Han. His father, a renowned blacksmith, was killed by the King of Han. After growing up, Nie Zheng fled to the state of Qi with his mother and sister to escape revenge for a killing, making a living as a dog butcher. Yan Zhongzi, an official serving in the court of Marquis Ai of Han, was at odds with his fellow prime minister, Xiang Le. It was said that Xiang Le was jealous of the virtuous and narrow-minded, always seeking to eliminate his political opponents. Unwilling to be harmed by Xiang Le, Yan Zhongzi left Han and traveled around various states, looking for someone who could assassinate Xiang Le for him.

When Yan Zhongzi arrived in Qi, he heard that Nie Zheng was a brave warrior who had become a butcher in Qi to evade enemies. Upon hearing this, Yan Zhongzi personally visited Nie Zheng's home, and they frequently interacted. One time, he brought many fine wines to Nie Zheng's house to celebrate his mother's birthday and presented a hundred yi of gold as a token of respect. Nie Zheng was surprised by such a generous gift and told him, "My family is poor, and with my mother still alive, I work as a dog butcher to provide for her. This is my duty, so I dare not accept such a valuable gift from you." Yan Zhongzi dismissed the people around them and said to Nie Zheng, "I have an enemy, and to escape him, I have traveled through many states. Now that I am in Qi, I heard you are a man of great righteousness. Therefore, I offer these hundred jin as your daily expenses. I am very pleased to have made a friend like you and have no other demands." Nie Zheng replied, "The reason I have given up my ambitions and am content to live in this small place as a dog butcher is to support my elderly mother. As long as my mother is alive, I dare not risk my life." Later, Yan Zhongzi repeatedly offered Nie Zheng lavish gifts, but Nie Zheng consistently refused to accept them. Nevertheless, Yan Zhongzi always treated him with great courtesy, observing all proper etiquette before leaving.

A few years later, Nie Zheng's mother passed away. After observing the mourning period for his mother, Nie Zheng said to his sister, "Alas! I, Nie Zheng, am merely a commoner, spending my days butchering meat. Yet, Yan Zhongzi, a minister of a feudal lord, traveled a thousand li to befriend me. He offered such a generous gift for my mother's birthday; though I did not accept it, he knew I was grateful. A virtuous person trusts a man from a humble background for a small act of righteousness. So, I, Nie Zheng, cannot betray his kindness. A few years ago, Yan Zhongzi asked for my help to eliminate his enemy, but because my mother was alive, I could not agree. Now that my mother has lived out her natural years, I should do something for my true friend."

Nie Zheng traveled west to Puyang and met Yan Zhongzi, telling him, "Previously, I did not accept your request because I had to support my mother. Now that my mother has passed away at a ripe old age, please tell me who your enemy is!" Yan Zhongzi said, "My enemy is Xiang Le, the prime minister of Han, and Xiang Le is the uncle of Marquis Ai of Han. His household has many guards, and his residence is heavily fortified. I have tried to send assassins, but none have succeeded. Since you are now willing to undertake this task for me, I will arrange some chariots and escorts as your assistants!" Nie Zheng replied, "Han and Wei are not far apart. To assassinate the prime minister of Han, who is also the ruler's uncle, cannot be done with many people. If too many go and even one is captured, the secret will be revealed, and everyone in Han will become your enemy. Wouldn't that also mean your downfall?" Nie Zheng firmly refused any chariots or escorts and went alone to assassinate Xiang Le.

When Nie Zheng arrived in Han, a strange phenomenon appeared in the sky: a white rainbow pierced the sun. People believed that a major event was about to happen. At that moment, Xiang Le, the prime minister of Han, was in his residence, protected by many warriors. Nie Zheng entered his mansion without a word, drew his sword, rushed straight in, and ascended the steps to assassinate Xiang Le. His actions terrified the guards nearby, who were momentarily bewildered and fell into disarray. Nie Zheng took advantage of their shouts and confusion, striking Xiang Le with a single sword thrust, killing him. He then killed dozens of other people. However, more and more people surrounded him, and seeing that he could not escape alive, he disfigured his face and disemboweled himself.

To find out who had dared to instruct an assassin to kill the Prime Minister of Han, the people of Han exposed Nie Zheng's body in the marketplace and posted a notice saying: "Whoever can reveal the assassin's identity and background will be rewarded with a thousand jin of gold." Nie Zheng's sister, Nie Rong, heard the news and told her neighbors, "This must be my brother." Then, Nie Rong went to the place in Han where the body was exposed. Upon seeing that the deceased was indeed her brother, she knelt by the corpse and cried loudly, "This is my brother Nie Zheng!" The person managing the reward said to her, "This man is the one who assassinated our Prime Minister of Han. Our ruler has offered a thousand jin to trace this person's information. Madam, do you not know this? Why do you still dare to claim your brother?" Nie Rong said, "I already know about the reward. However, my brother Nie Zheng abandoned his ideals and hid among common butchers because our mother was still alive, and I was not yet married. Now that our mother has passed away at a ripe old age, and I am married, my brother had nothing left to worry about. He took revenge for his true friend and calmly faced death. He disfigured himself to prevent people from identifying him, thinking of me still being alive! My brother considered me so thoughtfully; why should I fear implication and let his heroic name be obscured?" Nie Rong's brave act of recounting her brother's past deeds while caressing his body astonished the onlookers in Han. They were all moved by the chivalrous spirit of both siblings. Later, Nie Rong died of excessive grief beside Nie Zheng.