The story begins with a flashback to when young Se-ah and Geon-woo met in the elevator of their building. Geon-woo was immediately smitten with her. At school, some students started spreading rumors about Se-ah's parents' death, claiming she was cursed. However, Geon-woo, Na-ri, Ha-joon, and Hyeong-wook rallied around her, supporting her through the harsh whispers. Hyeong-wook even gave her his favorite toy to cheer her up. This is how the five of them became inseparable friends.
Fast forward to the present, the police have ruled Hyeong-wook's death a suicide. Despite this conclusion, Se-ah can't shake off the thought of his demise. She excuses herself from the nurse's office to go to the gym and fetch a fresh set of clothes. There, she comes across the toy that Hyeong-wook had given her when she first joined the school, triggering a vivid memory of their conversation the night before.
That night, she dropped by his place and insisted on giving him his birthday gift in advance since she wouldn't be able to attend his party. Hyeong-wook was visibly sad, but her visit managed to lift his spirits a bit. She explained that she had to start practicing over the weekend and assured him that the others would be there for his party. Hyeong-wook kept reiterating that Geon-woo wouldn't be coming. As she was leaving, he confided in her about a suspicious phone call he had received. Hyeong-wook knew it wasn't her on the other line, and he felt that she would never say those things about him.
Now, all his friends are grappling with their grief and shock in their unique ways. Se-ah runs into Coach Song at the gym, and they comfort each other. She panics when Coach Song mentions canceling the practice. She remembers that it was Geon-woo's wish, and if it comes true, he dies.
She tries to persuade Coach Song not to cancel practice, but an overhead light fixture falls between them as if it were a warning. Se-ah quickly checks the time as Geon-woo receives an alert that his wish has been granted. Like Hyeong-wook, he also gets a timer. Se-ah rushes to him, and they hold an impromptu meeting. Despite Se-ah's efforts to warn the others of impending danger, Na-ri refuses to believe it. She and Se-ah get into an argument, and Na-ri is offended that Geon-woo is siding with Se-ah.
According to Na-ri, Se-ah is the source of their misfortune due to the events that transpired with her parents. Se-ah confesses that she is tormented by witnessing her parents' final moments and cannot bear to see anyone she loves die. Ha-joon interjects, reminding them that they must find a solution. He attempts to delete the app from Geon-woo's phone and turn it off, but none of these efforts work; the app reinstalls itself, and the timer continues. They realize that even if they destroy the phone, nothing will change. Geon-woo's time is running out. They agree to meet at Se-ah's house to figure it out.
On the ride home, Geon-woo comforts her, and she admits that she wanted to quit the team after moving to town. It was Geon-woo who kept her spirits up and made her rethink her decision. At home, Se-ah heads to her aunt's place to shower while Geon-woo goes to his place. He receives a call from Se-ah and rushes to her place as he listens. On the phone call, he hears Se-ah mocking him and his feelings for her. By the time he arrives at her place, the call has disconnected.
He puts the phones in the fridge, worried that someone might be listening in on them. He realizes that she wasn't the one on the call and tells him about Hyeong-wook's call. The others soon arrive, and Ha-joon starts looking into the app's code. They hope to stop the timer and save Geon-woo. Unfortunately, their attempts fail.
Just then, Geon-woo starts acting strangely and says there's something in his eye. He starts desperately rubbing it and hits Se-ah when she tries to stop him. He suddenly points to a corner and asks if they also see someone there. Na-ri panics as soon as she turns, but the others see nothing. Things escalate as Geon-woo pierces his eye with his finger from a distorted angle.
He asks them to get out, and Na-ri hides in a corner and starts recording on her phone. Geon-woo starts bleeding from the nose as a girl hovers above, choking him. Ha-joon jumps to hold Geon-woo still while Se-ah calls for the police and ambulance. Once again, Geon-woo reaches out and slaps her. He turns to Ha-joon and starts choking him, blaming him for messing with the app and promising to kill them all. Ha-joon starts to struggle but soon passes out. To save him, Se-ah hits Geon-woo on the head with a laptop. He falls to the floor, bleeding profusely.
At the hospital, Se-ah stubbornly refuses to share with her aunt, a doctor by profession, the details of what transpired. Simultaneously, Geon-woo is battling for his life in the ICU.
Na-ri approaches Se-ah and informs her that Geon-woo's family is searching for her, blaming her for what happened without realizing she was trying to save Ha-joon. Na-ri offers to help her pack a few things, but Se-ah insists that her aunt has already taken care of everything. She shares the house password with Na-ri to allow her to retrieve her bag.
Meanwhile, Ha-joon is determined to shut down the app. A call from his sister, the shaman, warns him to halt his efforts, explaining that he only survived thanks to Se-ah. According to Ha-young, the children's interaction with a spirit called 'Jugu' has unleashed curses that can take various forms and currently manifest as a smartphone app. It spreads curses using something like a picture or video that carries someone's thoughts.
Ha-young urges Ha-joon to visit her, but he hesitates due to their previous fallout. As they converse, the snake hisses, and Ha-young's demeanor changes. In a concerned tone, she enquires about Se-ah and warns Ha-joon that she is in trouble.
The scene shifts to Se-ah writing a letter to Sa-ju as Geon-woo's condition deteriorates. This triggers her memory of her parents' accident. Unfortunately, by the time Ha-joon reaches the hospital, it's too late. Se-ah makes a wish to save Geon-woo and restore him to his former self before making the wish. She tells Ha-joon that she needs to uncover who is killing their friends to save them. The wish enables her to see the spirit that Geon-woo and Hyeong-wook encountered. Ha-joon confesses his sister's true profession and asks Se-ah to accompany him.
Ha-young senses impending danger and warns Bang-wool to prepare his knife. Suddenly, Geon-woo recovers, and Se-ah is elated to see her wish fulfilled. The episode concludes with Na-ri returning to Se-ah's house and discovering Geon-woo's phone. She compares the death timers on her phone and his, noticing an eight-hour difference. Suddenly, one of the timers stops.
