Detective Conan - Season 1 Episode 687 : The Unsolvable Ice Trap

Professor Agasa take the Detective Boys to visit an ice village. The mayor and his secretary boast about cancelling the winter festival to build a resort to bring in more income. The group stays overnight in the ice hotel. The next morning, the mayor staying in another part of the ice hotel is found strangulated in his bed. Professor Agasa reveals the culprit to be the ice sculptor using an ice melting trick to murder the mayor without leaving any evidence behind. The sculptor explains that he overheard the mayor and his secretary talk about murdering the previous mayor who suspected their embezzling the city's finances.