Kirie Goshima lives an ordinary life in Kurouzu-cho, until she witnesses Shuuichi Saito's father fixated on a snail shell. After sharing the incident with Shuuichi, he admits his growing urge to escape the town that he believes is plagued with spirals. However, the obsession proves fatal, leading to a string of inexplicable and terrifying events that drive the townspeople of Kurouzu-cho insane.