"Tragic Valentine" / "Valentine Murder Case" (Episode 6)

Conan runs into the black-clothed men from before on the Shinkansen bullet train. Upon investigating, he realizes they only resemble the two men. Using his new glasses and a bug, Conan overhears their conversation about a bomb in a black suitcase on board. He realizes that the suitcase is set to explode soon. Conan is able to narrow down the location of the suitcase leaving four suspects. Conan realizes that the woman on the cellphone mentioned how she liked viewing the mountains yet her seat was facing the sea. He realizes the black-clothed men's seats were facing the mountains, meaning she was the one who met them. Conan, with his new shoes invented by Agasa to increase kicking power, manages to kick the briefcase off the train before it explodes. The woman and the two men were later arrested.

SOURCE:

http://en.wikipedia.org/wiki/List_of_Case_Closed_episodes_(season_1)