"Beware Of Idols" / "An Idol's Locked Room Murder Case" (Episode 3)

Three days later, the Professor Agasa gives Conan the voice-changing bow-tie, and tells Conan that Rachel has been worried about Jimmy. After Conan's first day at school, his classmates Amy Yeager, Mitch Tennison, and George Kaminski plan to follow Conan home to befriend him. Later idol singer Yoko Okino arrives at Richard's agency asking him to investigate a suspected stalking. Once they arrived at Yoko's apartment, they find a dead man with a knife in his back. The man was revealed to be Yoko's high school boyfriend, making Yoko one of the three suspects, together with Yoko's manager and one of Yoko's rival in the show business. Conan investigates and finds out how the crime was committed. After knocking Richard unconscious with an ashtray, he impersonates Richard's voice with the bow-tie and reveals to the people at the scene of crime the man killed himself. He reveals the man created a block of ice with a knife inside it and laid on top of it until the knife was in his back. Later that week, after knowing Rachel has been excessively stressful since Jimmy's disappearance, Conan gives Rachel a call and with his bowtie set to Jimmy Kudo's voice. He tells Rachel he is on a difficult case and will return when it is solved.

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