Soo-hyun, a recent resident in a new neighborhood, decides to purchase a second-hand washing machine through a popular app. However, upon delivery, she discovers that the machine doesn't work. Frustrated by the seller's lack of responsibility, she leaves a scathing comment and reports the incident to the authorities. Unbeknownst to her, the seller is actually a dangerous serial killer who preys on unsuspecting victims through online platforms. Her public comment disrupts his plans, making her the next target of his sinister intentions. Soon, she begins to receive menacing phone calls, mysterious food deliveries, and unwelcome visitors at her doorstep. A visit to the seller's listed address unveils a horrifying truth when Soo-hyun and the police stumble upon a chilling discovery - a lifeless body.