Agasa takes the Detective Boys with him to a sauna as he fixes his product. At the sauna, the kids are introduced to four cast members filming a drama about a hitman. Since the sauna is crowded, the kids decide to bathe in the early morning. As they head to the sauna, Ai and Ayumi discover the Ganji Tetsuyuma, the scriptwriter, dead. The police arrive and conclude that Tetsuyuma slipped on a bar of soap and hit his head on the rocks. Conan reveals it was a murder and points out that water on the victim's body reveal the culprit washed something off and deduces it to be blood. The police assume the culprit waited at the verandah for the victim before committing the murder and begin searching for people entering the sauna without alibis; the suspects are the three other cast members.