A brainy teen whose impressive intellect sets her apart from the pack embarks on a desperate search for her missing sister in first-time director Takeshi Furusawa's atmospheric frightener. Nana's sister Noriko has gone missing after discovering what appeared to be a "lost" railway pass. When Nana discovers that another area teen had recently disappeared after making a similar discovery, the concerned girl recruits a classmate with a mysterious bracelet and a recently suspended train conductor to aid her investigation. As rumors of spectral figures on the tracks begin to proliferate, the curious trio discovers a cavernous passageway housing a dark and terrifying secret.