The Detective Boys attend a firefly festival to commemorate a shinto shrine in a village. The truck soon arrives with the fireflies and they are released into the fields. Later one of the truck drivers, Tokurou Nakamine, is found murdered and three of the villagers are the prime suspects. Conan notices a flashlight Genta found inside the truck and realizes who the murderer is. Using Agasa, Conan reveals the second truck driver, Shuchirou Tarumi, to be the murderer. Conan reveals that Tarumi murdered Nakamine in a desolated location near the village before turning the truck around and meeting with the other villagers. As evidence, Conan reveals the flashlight Genta found was actually a dictation machine with Nakamine's voice recorded on it. Tarumi takes Haibara hostage and attempts to flee but is eventually apprehended. Conan reveals that Tarumi's was tried of being blackmailed by for embezzling money from the firefly project and Nakamine's company and thus motivated his murder.
