Invited by Sera, Conan visits the Haido Hotel, where he encounters a series of hotel bombings. With the help of the hotel's legal adviser, Kisaki Eri, who happens to be passing by, Conan and Sera obtain past codes and narrow down the rooms where the bombs are likely to be to six. The possible culprits are Moriko, a hotel cleaner, Kureishi, a bellboy, and Hayashizaki, a guest in the room where the code was placed. With the time limit until the explosion approaching, will Conan and Sera be able to track down the culprit?