Sonoko's acquaintance Chikada Eimi of Orihime Club invites her to investigate pranks, to which Ran and Conan get dragged along. Before each prank, warning letters are sent to Club Orihime warning them of the pranks. That morning they received a letter stating, "EC will be brought to justice!" The letters are the initials of the victim. At the scene of the crime, they find a new letter stating, "TB dies as sundown tonight!" Only two hours remain until sunset. To prevent another incident from occurring, Conan and his friends search for a student with the initials TB.