The antidote to the APTX 4869 begins to wear off and Shinichi is about to change back to Conan. Ran holds onto him and refuses to let him go. As Shinichi attempts to find a way to hide and change back to Conan, Ran is tranquilized by Haibara and Shinichi is able to become Conan again without anyone noticing. The Detective Boys are on a camping trip when Professor Agasa's car runs out of gas, stranding them in the middle of the mountain. A man named Gouki Sudou drives by and refuses to help their situation. Soon after, the Sodou drives to his home atop the mountain and an explosion occurs. The Detective Boys arrive to find Sudou dead. The police investigate and declare the death as an accident caused by a lit cigarette and spilled gas which vaporized in the garage. As the police interrogates Sodou's wife, Ena Ginbayashi, Conan reveals Sudou was not smoking a cigarette and that something else caused the explosion. Due to Ena's consistency with her story, Conan deduces the explosion was a planned murder by Ena.
