Kazuyuki Kawai invites Kogoro, Ran, and Conan to his houseboat for dinner and to view the fireworks. During the fireworks, Kawai's guest, Tsuneo Yamasaki, is found dead from electrocution. Kogoro deduces that Tsuneo slipped on some water causing his fishing rod to touch exposted electrical wiring causing his death. Conan investigates and realizes its a murder.
After tranquilizing Kogoro, Conan using his voice changing bowtie, reveals the murderer to be Kawai. He reveals that Kawai set up the fishing rod so it would be caught at the bow of the boat. When the fishing rod is in place, Kawai asks Yamasaki for help to pull the fishing rod loose. As Yamasaki tries to reel in the hook, Kawai pushes Yamasaki causing the fishing line to cut due to a positioned razor blade and caused Yamasaki to fall backwards with the fishing rod which touches the exposed wiring. As evidence, Conan reveals that rubber should be found in Kawai's lighter as he used it to melt the rubber off the wires to set up the murder.
