King Kaolie of Chu had no son. Lord Chunshen was troubled by this and sought women likely to bear children, presenting many of them to the king. None bore a son.
Li Yuan, a man from Zhao, was grooming his younger sister to present to the King of Chu, but heard the king was unlikely to produce an heir and feared she too would fail to gain favor. Li Yuan sought employment under Lord Chunshen as a retainer. After some time he requested leave to go home, and deliberately returned late. When he came back and reported, Lord Chunshen asked why.
"The King of Qi sent an envoy to seek my sister's hand. I was drinking with the envoy, so I missed the deadline."
Lord Chunshen said: "Has the betrothal been finalized?"
"Not yet."
"May I meet her?"
"You may."
Li Yuan then presented his sister, and she became Lord Chunshen's favorite. When she discovered she was pregnant, Li Yuan and his sister plotted together.
Li Yuan's sister found a private moment and said to Lord Chunshen: "The king's favor toward you surpasses even that toward his own brothers. You have served as Chu's minister for over twenty years, yet the king has no son. After the king's death, a brother will be enthroned. Once that happens, each new king will elevate his own former allies — how will you retain your position? And it is not merely that: having held power for so long, you have slighted the king's brothers on many occasions. If a brother truly takes the throne, disaster will reach your person. How will you protect your ministerial seal and your fief in Jiangdong?
"Now I know I am with child, though no one else knows. I have been your favorite for only a short time. If, by virtue of your influence, you present me to the King of Chu, and the king takes me as his favorite — should Heaven grant me a son, then your child will be king. All of Chu's fiefs will be yours. Is that not better than facing unpredictable calamity?"
Lord Chunshen was fully convinced. He moved Li Yuan's sister to a proper residence and spoke of her to the king. The king summoned her, took her as his favorite, and she bore a son. The boy was made Crown Prince and Li Yuan's sister was made queen. The king honored Li Yuan, and Li Yuan took charge of affairs.
Once Li Yuan had installed his sister as queen and her son as Crown Prince, he feared Lord Chunshen would let the truth slip and grew increasingly arrogant. He secretly cultivated assassins, intending to kill Lord Chunshen to silence him. People in the state were somewhat aware of this.
Lord Chunshen had served as Chu's minister for twenty-five years when King Kaolie fell ill. Zhu Ying said to Lord Chunshen: "The world has unexpected blessings, and it has unexpected disasters. Now you exist in an unpredictable world, serving an unpredictable lord. How could there not be unpredictable men?"
Lord Chunshen said: "What are the unexpected blessings?"
"You have served as Chu's minister for over twenty years. Though your title is prime minister, you are in practice the King of Chu. Your five sons all serve as ministers in other states. Now the king is gravely ill and may die any day. The Crown Prince is young and weak. Should the king die and you serve as regent to a young ruler, you could assume authority like Yi Yin or the Duke of Zhou. When the king comes of age, return power; if not, simply face south and call yourself sovereign, and Chu is yours. These are the unexpected blessings."
"What are the unexpected disasters?"
"Li Yuan does not govern the state — he is merely the king's brother-in-law. He holds no military command, yet he has secretly maintained assassins for a long time. When the king dies, Li Yuan will be first through the gate. He will seize the initiative, control the deliberations, and cut off your fate — wielding power to kill you and silence you. These are the unexpected disasters."
"What are the unexpected men?"
"Appoint me first as a palace guard. When the king dies and Li Yuan enters first, I will stab him through the chest and kill him for you. These are the unexpected men."
Lord Chunshen said: "Let it go, sir. Say no more. Li Yuan is a soft, weak man. And I am on good terms with him. How could things come to that?"
Zhu Ying was frightened and fled.
Seventeen days later, King Kaolie died. Li Yuan did indeed enter first. He stationed assassins inside the Thorn Gate. Lord Chunshen entered after, and at the Thorn Gate, Li Yuan's assassins attacked from both sides, stabbed Lord Chunshen, cut off his head, and threw it outside the Thorn Gate. Officials were then sent to exterminate Lord Chunshen's entire family.
Li Yuan's sister — who had first become pregnant by Lord Chunshen and then been presented to the king, whose newly born son was in fact Lord Chunshen's — saw that son enthroned as King You of Chu.
That same year, the First Emperor of Qin had been on the throne for nine years. Lao Ai had also staged a rebellion in Qin; it was discovered, his three clans were exterminated, and Lu Buwei was deposed.