Shinichi, Ran, Kogoro, Ayumi, Genta, and Mitsuhiko are traveling on a train, when Shinichi spots to men dressed in black. Thinking that these men are the same people who had shrunk him using APTX4869, he plants a bug, which Dr. Agasa had created, in their seat. However, he realizes that he is mistaken.
While testing out the bug that Dr Agasa had given him, Shinichi learns about a bomb that was brought aboard a train. He yells out “Multiple!” in response to the conversation between the two men, which attracts their attention. However, he also yells out a math problem to make the men feel at ease.
After trying to tell the conductors to get everyone off the train and failing, It is up to Shinichi to find the bomb with the few clues he had obtained from the conversation between the two men in black.
