Dong-jin runs into Mi-jung, the girl who was branded as a witch in their high school. He follows her to her home without realizing it and sees how she's still suffering from the curse she's rumoured to have. Dong-jin decides to find out the law of the curse so he can help lift it and save Mi-jung.

Mi-jung, who couldn't stand the rumour of her being a witch and the boys from the same school getting hurt and dying, drops out of school. But the same rumour spreads in her village, leaving her no choice but to hide from everyone. Her father decides to take her to Seoul, but an unfortunate accident kills her father as well.

Dong-jin joins the statistics class and befriends Joong-hyuk at university, and they become best friends. He writes a statistics report to prove Park Mi-jung is not a witch, gaining the professor's attention. Dong-jin returns home during school break but learns the villagers have ousted Mi-jung from the village, breaking his heart. After graduating, he gets a job with Shine Solutions and becomes successful.

The statistics report Dong-jin wrote returns to him after his mother's death, and a battle within himself begins. He takes time off work and finds a place to live next to Mi-jung to get closer. Meanwhile, a victim of Dong-jin's work comes to get his vengeance, which makes him realize numbers aren't the answers to everything. Afterward, he returns to his hometown to find clues that will break Mi-jung's witch's curse.

Dong-jin returns to Taebaek in search of a clue that could break the witch’s curse on Mi-jung. With the support of his friends, he meticulously compiles information about the string of accidents and uncovers a disturbing pattern. As he digs deeper, he realises that he meets every condition of his hypothesis, leaving him filled with suspicion and uncertainty.