Everyone All previously who were young guys grow a moustache! I wish Episode 39 tells us which year we’re at now, but no, we’re supposed to guess (hey, this is so foreigners unfriendly). From the dialogues, we learn that this is a few years after the First Manchu Invasion of Joseon (1627), which puts us at somewhere in the 1630s.
Jung-myeong is now a mother of three, giving birth to her third son at the beginning of Episode 39. Crown Princess Minhoe also gives birth to her first son, which is a happy news for the royal family, as this is the first royal grandson of Injo (a check with Wikipedia tells us it is in the year 1636).
Despite happy news of addition of new family members all around, Joseon was in the middle of recovering from the First Manchu Invasion, with many Joseon people still held as hostages by the Jurchens. Because some of the hostages are family members of the yangbans, who’re willing to pay a large sum of money to the Jurchens to have their family returned, the Jurchens begin to demand exorbitant ransoms from the Joseon society in exchange for the release of the peasants.
Many of these hostages escape from Jurchen, only to be returned back to Jurchen by Joseon officials, in fear that Jurchen will use it as a reason to attack Joseon again, if they accept the hostages. Jung-myeong and Crown Prince Sohyeon (Baek Sung Hyun) work together in secret to intercept the return of those hostages who escaped, to Jurchen, incurring the wrath of Kang Joo-seon and Kim Ja-jeom, who I think are making use of the paying of ransoms to Jurchen, as a mean of establishing ties with Jurchen.
Jo Yeo-jung got wind of the secret alliance between Jung-myeong and Sohyeon, and plots to have Sohyeon fall out of favor with Injo, who has been increasingly relying on Sohyeon. The relationship between Injo and Jung-myeong is still sour, and Yeo-jung, now a royal consort (Queen Inyeol has since passed away), hopes to remove Sohyeon from the picture in order to regain Injo’s trust in her and Kim Ja-jeom. Not only Yeo-jung, Kang Joo-seon is also hoping to get rid of Sohyeon, and extends his claws to Grand Prince Bongrim (Lee Minho, the younger one).
Yeo-jung works with Kang’s wife, and feeds Injo with the seeds of doubt about Sohyeon working together with Jung-myeong, which made Injo flare up, and messed up the allegiance ceremony held with the Jurchens (by now they actually call themselves Qing). It is tantamount to another attack from Qing, as it is disrespect for Hung Taiji, the Qing Emperor.