This 2012 Korean film, based on the webtoon of the same name by Kang Full, was directed by Cho Geun Hyun in his directorial debut. Kim Sae-ron

) takes that common urban anxiety and turns it into a chilling masterpiece of suspense. Based on a popular webtoon by Kang Full, this film isn't just about a serial killer—it's a biting look at communal apathy and the secrets we keep behind closed doors. The Plot: A Killer in Plain Sight

After decoding:

(Kim Sung-kyun), continues to live in the building, various neighbors notice disturbing clues: The Pizza Delivery Boy