The heirloom incense burner of the Kumado family, a prominent local family, is stolen. The thief returns the incense burner, but Detective Yamane follows Kogoro's theory that a member of the family is the thief and thoroughly investigates the alibis of Iwao, Makie, Soichi, and Junji. Conan finds Naomi's alibi odd and questions her uncle Adachi. According to him, two years ago Naomi witnessed Shuko meeting with a man on the Tottori sand dunes and had been using the information to blackmail her. Hearing Adachi's story, Conan realizes why Shuko had been tied up and draws closer to the truth behind the case... However, the real crime is about to occur...