Episode 1 of The WONDERfools unfolds in the picturesque town of Haeseong, where Eun Chae-ni, a 27-year-old with a zest for life, learns the devastating news that she is terminally ill. Her heart breaks as she confronts her grandmother, Kim Jeon-bok, who denies her request for financial assistance to embark on a world tour. Simultaneously, Lee Un-jeong, a dedicated civil servant, witnesses Chae-ni stealing a young boy's ice cream. His colleague dismisses her as an eccentric and urges Un-jeong to steer clear.
That night, Kim Bong-pal, a ragged scavenger, finds himself trapped in a slimy puddle at the dump. His ear melts off in the contact with the slime, and he collapses unconscious.
Days later, Bong-pal's friend reports him missing at City Hall and asks Un-jeong's colleague for help. The man ignores the request and asks him to leave. Meanwhile, Son Gyeon-un arrives to lodge another complaint about the dump where Bong-pal disappeared.
Exasperated by his persistent grievances, Un-jeong is tasked with handling the matter. He informs Gyeon-un that they cannot intervene as the dump is private property. Gyeon-un seethes in anger and threatens to report Un-jeong to his superior, but Un-jeong stands firm, forcing Gyeon-un to retreat.
Outside the office, an old man approaches Un-jeong and warns him that people have been vanishing from their town. He claims that similar incidents occurred in Haeseong two decades ago. Later that day, members of a religious cult kidnap the old man and whisk him away.
Meanwhile, Chae-ni pleads with her grandmother once again for permission to travel. Jeon-bok refuses, and Chae-ni's desperation for funds prompts her to flee to Mount Kilimanjaro. She begs her neighbor and friend, Kang Ro-bin, for money but learns that he has already spent all his savings fixing the leaky roof of his rental apartment due to his landlord's inaction. Chae-ni decides to leave regardless and begins preparations for her escape. She procures supplies from a hardware store where she encounters Un-jeong, who is also shopping for essentials. Both Chae-ni and Un-jeong eye each other's shopping carts suspiciously.
As Chae-ni exits the store, she struggles with her heavy suitcase and attempts to use Bong-pal's abandoned cart. Un-jeong follows her, convinced that she might be a serial killer after hearing the old man's warning. He seizes the suitcase from her hands, causing it to burst open to the embarrassment of both parties. To his surprise, the suitcase contains only Chae-ni's clothes. Un-jeong awkwardly helps her repack and hands her his business card. Chae-ni promises to contact him later for compensation for the damages he caused.
Meanwhile, Gyeon-un returns home to his domineering wife, who is enraged that he failed to file the complaint properly. She insists that the dump is harming their flower business. Gyeon-un suggests sending his mother abroad for her birthday, but his wife refuses to take out a loan for the trip.
Later, Gyeon-un picks up his daughter from school, but she ignores him due to the slippers he is wearing. He then visits Ro-bin's leaky apartment, where the two men bond over their financial troubles. Shortly thereafter, Chae-ni arrives and offers to pay them if they help him with something.
Elsewhere, Un-jeong receives a noise complaint from his downstairs neighbor. It is revealed that he has been secretly investigating the Wunderkid Project. He later visits a group of homeless men while searching for the old man from City Hall. There, he discovers a brochure connected to a religious cult and decides to investigate further. The kidnapped old man wakes up inside a locked room.
Meanwhile, Chae-ni convinces Gyeon-un and Ro-bin to help stage her kidnapping. The trio films a fake ransom video to send to Jeon-bok. However, while tied to a chair, Chae-ni suddenly dies. Gyeon-un and Ro-bin panic after realizing that she is dead. At the same time, Jeon-bok begins worrying about Chae-ni and asks an ex-cop named Gu Jun-mo to search for her.
Instead of taking Chae-ni's body home, Gyeon-un pressures Ro-bin into dumping her body at the same dumping yard connected to Bong-pal's disappearance. However, they run into Un-jeong, who demands to inspect the wheelbarrow they are hiding.
During the struggle, Gyeon-un and Ro-bin accidentally shove the wheelbarrow forward, causing Chae-ni's body to roll into the same slimy puddle that Bong-pal fell into earlier. Ro-bin and Gyeon-un desperately try to stop Un-jeong from seeing the body, and both men end up falling into the slime while Un-jeong remains dry.
Suddenly, Chae-ni's body disappears. Terrified, Un-jeong threatens to call the police, but Gyeon-un tries to stop him. Moments later, the emergency operator calls back and sends officers to investigate the scene. Un-jeong tells the cops that Gyeon-un and Ro-bin were attempting to dump Chae-ni's corpse. However, the officers point out that Chae-ni is standing right behind them, leaving all three men shocked.
A flashback from earlier that day reveals that Un-jeong used his special powers to protect Chae-ni from being injured by the sharp objects inside her suitcase as the episode comes to an end.
