The producer of the accusation program begins to track the cult 'Samsundo' and the historical facts behind it. The more they try to find out about 'Samsundo', the more they become engulfed in a bizarre phenomenon. Will they be able to safely arrive at 'Thousand Years' Shrine, the only shrine in Korea, and let the whole story known to the world?

Yu-mi and her friends are staying in a small Japanese town. When Hee-jung doesn't return home for dinner, they decide to visit the shrine from her painting. Strange occurrences startle them as they explore the shrine, even some end up injuring themselves. Yu-mi senses a sinister presence lurking within. She knows the right person for this, her old shaman friend named Myung-jin. Leaving the past behind with Yu-mi, he joins Pastor Han-ju, a spiritual leader of the town. Their mysterious cooperation to keep everyone safe is about to begin.

Eighteen-year-old Da-seul was spending an ordinary life helping her father run a traditional makgeolli (rice wine) brewery. However, because the origin of the 'nuruk' (the yeast) that determines the taste of the makgeolli was unknown, their makgeolli could not be officially distributed, and they ended up secretly selling it only to the local villagers. Her older brother, Da-hyeon, who wanted to modernize the brewery, secretly threw away the old nuruk and replaced it with a commercially available one without telling their father or Da-seul. He thought no one would notice—but from that day on, Da-seul fell ill as if possessed, saying "the nuruk is gone." At first, Da-hyeon found it absurd, but as Da-seul's condition worsened, he began to take it seriously. He eventually discovers traces of the nuruk in an unexpected place, and through a chaotic episode involving homeless people, Da-seul and Da-hyeon come to face a truth they had long turned away from.

Woojin, a man guided by his deepest desires, finds a broken guitar left behind by a mysterious man after failing an audition.

Humming centers around the relationship between a sound engineer and a supporting actor working on the post-production of an unfinished film, along with the anecdote of a deceased actor.