Widowed Welsh mother Anna Loenowens becomes a governess and English tutor to the wives and many children of the stubborn King Mongkut of Siam. Anna and the King have a clash of personalities as she works to teach the royal family about the English language, customs and etiquette, and rushes to prepare a party for a group of European diplomats who must change their opinions about the King.

On the eighth of April of King Gyoeng-deok's 10th year of the reign of the Unified Silla Period, Guseulagi, a daughter of Yu Jong, joins the king's parade to Bulguksa Temple, where she meets a stonemason named Asadal from Buyeo. Having a crush on him, she visits Sakyamuni Pagoda, a masonic site; only to find that Asadal had broken down from exhaustion. While she takes care of him, her love for him grows. But Asadal misses his wife who is waiting for him in Buyeo. Meanwhile, Geum Seong who has a crush on Guseulagi, asks his father, Geum Ji, to propose on behalf of him. But Yu Jong is so dissatisfied with Geum Ji because he is a treacherous subject, that he turns down the proposal, instead of hurrying up his daughter's marriage with Gyeongsin, a faithful subject. Asanyeo who has been waiting for her husband Asadal in Buyeo goes to Bulguksa Temple after her father-in-law had died.

Deep in the Valley interlaces a story of young romance set in Yanaka (part of old downtown Tokyo) with a Japanese period drama based on Five-Story Pagoda, a classic literary work by Rohan Koda. In the contemporary story, Kaori, a young woman working for a non-profit organization that restores home movies, learns that there used to be a five-story pagoda in the middle of Yanaka Cemetery. It burned down in 1957, and rumor has it that someone has an 8mm film of the fire.