A series of cat killings occurs in a certain neighborhood. The suspect is surprisingly Baek Si-yun, a third-year middle school student who ranks first in his entire school. When Si-yun is pushed into a situation where no one believes him despite his claims of innocence, he sets out to find the cat killer himself, along with his friends Su-min and Jeong-hyeon, who are the only ones who trust him. However, in the process of searching for the killer, he becomes entangled with Auntie Hwa-ja, who works at an animal shelter, and Jun-woo, a detective loitering around her. This pulls them all into an uncontrollable whirlwind of events...