It’s another milestone for Royal Secret Agent, as its tenth episode surpassed the 10 percent viewership mark and recorded 7.7 and 11.6 percent ratings. After infiltrating the secret banquet, Sung Yi-gyum (Kim Myung-soo), Hong Da-in (Kwon Na-ra), and Park Chun-sam (Lee Yi-kyung) chase after the main culprit of the killings.
Kang Soon-ae is auctioned off
In the middle of the banquet, Kang Soon-ae (Jo Soo-min) is auctioned off to be the leader’s concubine for 500 coins. Enraged, Yi-gyum reveals his identity and chases after the leader and Soon-ae. Led by Da-in, the royal soldiers awaiting Yi-gyum’s order outside charge inside and arrest everyone. Sung Yi-beom (Lee Tae-hwan) arrives at the banquet, but the leader has already escaped with Soon-ae.
Park Chun-sam, the master of impersonation
Da-in finds a way to trick the arrested scholars into confessing. Using the goblin mask, Chun-sam pretends to be their leader who has come to rescue them. Overjoyed, they rush towards him and call him by his name. The leader turns out to be the magistrate (Han Dong-gyu, Memorials) all along, who is responsible for all the killings in the town.
The royal secret agent saves another town
The magistrate subdues Yi-gyum and locks him in a cellar along with Soon-ae. He then orders his soldiers to kill Da-in and Chun-sam, but Yi-beom arrives in time and saves them by lying that the royal agent’s soldiers have the place surrounded. Desperate, the magistrate takes Yi-gyum hostage. Da-in attempts to shoot him, but knowing her terrible archery skills, Yi-gyum begins to fear for his life. Da-in’s arrow misses, but it distracted the magistrate long enough for Yi-gyum to tackle him down. With the enemy arrested, another town has been freed from tyranny.
Sung Yi-gyum parts with Kang Soon-ae once more
As they part, Yi-gyum asks Soon-ae what happened in the past, but Soon-ae lies that she and Yi-beom have become lovers. In truth, their town magistrate desires for Soon-ae to become his concubine. Soon-ae refused, angering the magistrate who ordered that she be killed. Yi-beom freed her out of prison, and they escaped together. After knowing that Yi-gyum is an agent, Soon-ae decides to part ways with him so Yi-gyum can keep pursuing his dreams.
Hong Da-in weeps for her late father
Back in Hanyang, Kim Byeong-geun (Son Byung-ho) reports to the King (Hwang Dong-joo) what he found in Jang Tae-seung’s (Ahn Nae-sang) house. Enraged, the King orders that Yi-gyum and Da-in return to Hanyang for interrogation. Meanwhile, en route to Jeolla province, the three pass by the very place where Da-in’s father, the late Prince Hwiyeong, has taken his life. Da-in weeps and pays her respect.
The team sets off for their last mission
In Jeolla province, the team’s last mission is to talk to Governor Kim Myeong-se, who has been struck with a skin disease. To get near the governor, Yi-gyum and Chun-sam plan to enlist as provincial soldiers, while Da-in volunteers to be a book reader for the governor.