The Mansion of Horror (恐怖の館,Kyōfu no Yakata?) is the 17th chapter of the manga of Detective Conan. It was written by Gosho Aoyama, drawn by him and his assistants and first released in Shōnen Sunday #21-22/1994 on May 11th, 1994 and later on reprinted as part of Volume 2 on July 18th, 1994. It was released in English by Viz Manga on November 3, 2004 under the name Mansion of Horror.
At school, Conan's classmate Ayumi invites him to go ghost-hunting with her and Genta at a supposedly haunted mansion. While both Conan and another classmate, Mitsuhiko, express skepticism at the existence of ghosts, they end up coming along. At the mansion, Genta reveals a hidden entrance that gives the access to a door, which is unlocked. Ayumi has second thoughts due to the dark interior and onset of rain, until thunder scares her to run inside. She trips and gets dirty from the dust, but is able to clean up in a nearby bathroom. While exploring, a door seems to open on its own, but it turns out to be due to an open window. Mitsuhiko goes to use the bathroom, and after hearing a strange noise forces himself to be brave and investigate. He discovers stairs leading down to the basement, and follows the sounds to a well-lit room. Upstairs, the other three hear Mitsuhiko scream and rush to investigate.