Metropolitan Police Detective Love Story 8 Left Hand's Ring Finger Meitantei Conan : Season 1 Episode 487

Kogoro is invited to attend an interview of the mystery book writer Masataka Moroguichi. The next day, Moroguichi is found dead from consumption of poison. The room was locked and the key was in Moroguichi's palm; The only opening to the room is a small window which can only fit a small child.