Prince Dan of Yan was originally the crown prince of the Yan State, but was later sent to the Qin State as a hostage, where he endured great humiliation and secretly fled back to Yan. Seeing that Qin was about to annex the six states and unify the realm, Prince Dan was filled with fear and sought help from his Grand Tutor, Ju Wu. However, faced with such a situation, Ju Wu was also at a loss for what to do.
Not long after, Fan Yuqi, a general of the Qin state, fled to the Yan state. It turned out that Fan Yuqi had been ordered by King Ying Zheng of Qin to attack the Zhao state, but he was defeated by the Zhao general Li Mu. Fearing that the King of Qin would blame him, he dared not return to Qin and instead escaped to Yan, begging Crown Prince Dan to take him in. Ju Wu advised the Crown Prince not to agree to his request, lest it anger the King of Qin and bring disaster upon them. However, Crown Prince Dan was determined to let Fan Yuqi stay. Seeing this, Ju Wu said no more. Afterward, Ju Wu suggested that the Crown Prince appoint a strategist named Tian Guang to help devise a plan to protect the state.
When Tian Guang visited, Crown Prince Dan treated him with courtesy and asked him how to protect the State of Yan from the threat of Qin. By then, Tian Guang was advanced in years and felt too old to contribute much to his country, so he recommended his close friend Jing Ke to the crown prince. Jing Ke was originally a knight-errant from the State of Wei and had always shared a strong bond with Tian Guang. Crown Prince Dan decided to summon Jing Ke and asked Tian Guang to convey his intentions to him. As Tian Guang took his leave, the crown prince, fearing that news of their meeting might leak out and bring unnecessary trouble, specifically urged him not to mention this matter to anyone else.
After bidding farewell to Crown Prince Dan, Tian Guang went to visit Jing Ke and told him that he had recommended him to the prince, urging him to meet with the prince no matter what. Jing Ke readily agreed to his request. Tian Guang was deeply relieved and said to Jing Ke that he had promised the prince he would never disclose their meeting. Now that Jing Ke had agreed to see the prince, his wish was fulfilled, and he would have no regrets even if he took his own life immediately. With these words, Tian Guang slit his throat in front of Jing Ke. Deeply moved by this, Jing Ke was later influenced to take the desperate risk of assassinating the King of Qin, at least in part due to the impact of Tian Guang's death.
After meeting with Crown Prince Dan, Jing Ke recounted Tian Guang's death and its cause. The Crown Prince, shedding tears, expressed gratitude for Jing Ke's arrival. During this meeting, he proposed the plan to assassinate the King of Qin, hoping Jing Ke would undertake this great mission. Jing Ke remained silent for a while before stating that he was of mediocre talent and feared he might fail to meet the prince's expectations. Despite this polite refusal, Crown Prince Dan refused to give up; the crown prince of the mighty Yan State actually knelt and kowtowed to Jing Ke, a commoner, begging him to accept the request.
Jing Ke did not decline further. Afterward, he settled in with Crown Prince Dan. To ensure Jing Ke would devote himself fully to his cause, the prince continuously won him over with treasures and beautiful women. For a considerable period thereafter, Jing Ke lived a life of luxury and indulgence. However, Crown Prince Dan never heard him mention the assassination of the King of Qin.
Later, as the Zhao Kingdom was also swallowed up by the Qin Kingdom and the Qin army approached the southern region of the Yan Kingdom, Crown Prince Dan could no longer hold back his anxiety and urged Jing Ke to act quickly. Jing Ke proposed that he bring the head of Fan Yuqi, a traitor to the Qin Kingdom, to meet the King of Qin, as only this could gain the king's trust, and then he would assassinate the king while he was off guard.
Although Jing Ke's words were very reasonable, Crown Prince Dan could not bear to betray his close friend Fan Yuqi and had to ask Jing Ke to find another way. However, Jing Ke insisted that this was the best method, and regardless of whether the Crown Prince agreed, he would proceed with it, even going behind the Crown Prince's back to secretly meet with Fan Yuqi.
By this time, Fan Yuqi's parents and clan had already been executed by the King of Qin. Fan Yuqi harbored a deep hatred for the King of Qin but could find no way to take revenge. Jing Ke then said to him that if he could bring Fan's head to meet the King of Qin, it would surely please the king, and then he would find an opportunity to kill him. In this way, he could avenge Fan's family and also protect the State of Yan from being destroyed by Qin. Deeply moved by Jing Ke's words, Fan Yuqi immediately committed suicide in front of him. When Crown Prince Dan heard of his death, he could not help but weep bitterly, but since things had come to this point, he had no choice but to proceed with Jing Ke's plan.
Obtaining Fan Yuqi's head alone was still not enough for Jing Ke. Before assassinating the Qin king, he had many preparations to make. First, he needed a sharp dagger, and to ensure the assassination succeeded, he had to coat it with the deadliest poison under heaven. Fortunately, Crown Prince Dan had already prepared all of this. The prince purchased what was said to be the sharpest dagger in the world from the renowned swordmaker Xu Furen for a hundred gold pieces. Notably, this so-called Xu Furen was actually a man—his surname was Xu and his given name was Furen. After acquiring the dagger, the prince ordered it to be coated with some unknown lethal poison. It was said that if a person's blood came into even the slightest contact with this poison, they would die instantly.
By this time, the preparations for assassinating the King of Qin were complete. Jing Ke took Fan Wuji's head and a dagger, and together with his assistant Qin Wuyang, set off on the irreversible path to assassinate the King of Qin. The Crown Prince, dressed entirely in white mourning clothes, rushed to the banks of the Yi River to see him off. As he departed, Jing Ke sang loudly: "The wind blows bleakly, the Yi River is cold; the brave man leaves, never to return!" This timeless Song of the Yi River, which has been passed down through the ages, also foreshadowed Jing Ke's tragic fate thereafter.
After arriving in the State of Qin, Jing Ke first went to pay respects to Meng Jia, a favored minister of the King of Qin, and expressed to Meng Jia that the King of Yan wished to present the King of Qin with the head of Fan Yuqi and part of Yan's territory, thereby demonstrating Yan's sincere submission to Qin. After Meng Jia relayed Jing Ke's words to the King of Qin, the king ordered an audience with Jing Ke at the Xianyang Palace.
On the appointed day, Jing Ke and Qin Wuyang arrived at the main hall of the Xianyang Palace carrying two boxes—one containing Fan Yuqi's severed head and the other holding a map of the Yan State. Overwhelmed by nervousness, Qin Wuyang couldn't help trembling all over. Jing Ke quickly and calmly covered for him, explaining that he was merely flustered because he had never faced such a grand occasion, causing him to lose his composure before the world-renowned King of Qin.
The King of Qin, suspecting nothing, ordered Jing Ke to present the map of Yan. Jing Ke slowly unrolled the scroll before the King of Qin, finally revealing
Subsequently, Jing Ke continued to chase the King of Qin, and the two of them circled around the pillars in the hall. Jing Ke was never able to stab the king, and was eventually wounded by the king's sword. Jing Ke fell to the ground with a leg injury, then threw his dagger at the king, but it struck a pillar instead. Having failed to assassinate the King of Qin, Jing Ke was immediately executed on the king's orders.
Jing Ke's assassination attempt on the King of Qin made the king deeply detest the State of Yan, so he sent his general Wang Jian to attack Yan, quickly capturing its capital. Forced into a corner, the King of Yan had no choice but to kill Crown Prince Dan and present his head to the King of Qin. However, the King of Qin was unmoved and continued to order attacks on Yan. Five years later, the State of Yan was completely destroyed by Qin.