Poong, the Joseon Psychiatrist

Se Poong's treatment of the Crown Prince gets him respect from His Majesty, and he gets the title "Divine Needle". However, things go terribly wrong when he treats His Majesty. Se Poong blames himself for the tragic outcome, but Yoo Hoo Myung, his father, looks further into the case and finds evidence of the king's poisoning. Unfortunately, Hoo Myung passes away without being able to close the case. With hardships piling up, Se Poong even gets exiled from Hanyang.

Se Yeob recognizes who the lady covered in blood is the moment he sees her. However, he is in no shape to save her himself. Not long after, Eun Woo is brought to Gyesoo Clinic again in a critical state. This worries Se Yeob, and he decides that he should look into whatever it is that's causing her to harm herself. Meanwhile, it seems like there is a reason why Granny keeps calling Se Yeob by the name "Poong".

The appearance of Gumiho tears up Sorak Village, but a little girl is accused of being Gumiho herself. Se-poong and Eun-woo look into the case, believing that a little girl could not have murdered two full-grown men. Meanwhile, a royal inspector dispatched to Sorak Village with a side task begins to look for a man named "Yoo Se-yeob."

Se Poong is flustered when his painful memories are brought up again right in front of him, and it torments him. Meanwhile, a lady suffering from hand tremors visits Gyesoo Clinic, and this eventually leads to a tragic situation for Man Bok. Unless Se Poong and the others do something quickly, Man Bok, Se Poong's only friend, might lose his life.

Time is ticking for Se Poong and Eun Woo to save Man Bok, and they struggle to reveal the truth behind Gae Ban's death. Meanwhile, a rumor starts to spread on the streets that the King's death was caused by a mysterious poisoning, and those who are behind the King's death begin to take measures to cover the tracks. 

Se Poong and Eun Woo make up for each other's shortcomings as they continue with their journey of treating and helping people in need. Sin Woo watches them from afar, and their intimacy is just too unbearable for him to handle. Meanwhile, the truth behind the night of the deceased King's death remains in the dark. 

Realizing that Haedongboncho has something to do with his father's death, Se Poong looks for anything that is related to it. While doing so, he also figures out that Gye Ji Han actually knows who he is and who his father was. In the meantime, Gyesoo Clinic is on the verge of being sold at an absurd price due to a secret that Ji Han doesn't want to reveal. 

As the plague spreads throughout Sorak Village, those who are infected are on the verge of being burned alive just for the purpose of stopping the contagion. While treating the neglected patients, even Eun Woo gets infected, and Se Poong chooses to risk everything to save her. Meanwhile, Ji Han seems to be the only one who knows enough about the plague, but he just won't say a word about it.

Sin Woo offers Se Poong a chance to run away before he takes Se Poong's life. However, Se Poong stands by his principles and decides to stay, believing that Gyesoo Clinic is now where he belongs. Meanwhile, Eun Woo gets assaulted by a stranger. While looking into the incident, Se Poong and Eun Woo both end up expressing the feelings they've been struggling to share. 

After hearing about Sin Woo's disappearance, Se Poong and Eun Woo feel that something just doesn't add up and start looking for Sin Woo and eventually find him in a fatal condition. While taking care of him in secret, an old friend of Se Poong's makes a surprise visit with an even more surprising message. At the same time, the opposing party looks for Se Poong to end his life. 

The truth is never easily revealed when people are risking their lives to hide it. The only person who knows and can prove the truth has died right in front of Se Poong's eyes, and it puts him in despair. However, nothing will make him back down unless he fulfils the duty given to him by His Majesty. Hanyang is his next destination, and this time Eun Woo accompanies him. Meanwhile, Commander Im proceeds with his plan to tear down Gyesoo Clinic.

Se-poong acquires all the proof he needs to bring the evil ones to justice. If he succeeds, this will allow him to clear his name. However, even with apparent evidence, the corrupted ones won't go down without putting up a fight. Meanwhile, seeing Se-poong risking everything to do what's right worries Eun-woo.