Nothing is more frightening, as the narrator points out, than a ‘time-rich nosy person’. Exhibit A is Ahn Geo-ul (Gyeong Su-jin), who commits herself to social justice causes with terrifying tenacity. After temporarily renting a unit in the Baek-sae Apartment building, she discovers that a loud, hard to locate banging noise occurs from 4am every night, making the residents’ liv…