Meitantei Conan S17E04 - Clash of Red and Black (Hades)

Kakuzo Okudaira's wife, butler, and maid are interrogated about their actions prior to Kakuzo's murder. Eisuke discovers the photo of his mother missing and returns to the pool where he slipped and fell earlier to search for it. He finds it at the bottom of the empty pool and when he climbs back up, Conan realizes something that helps him solve the case. Back at the crime scene, Kogoro still believes Kakuzo committed suicide. Conan stuns Kogoro to use him to reveal the trick behind the murder and explain that Kakuzo's dying message points to Kikuyo the maid who also murdered Kakuzo's son the year before using a similar trick. Kikuyo confesses and explains she murdered them because they murdered their former butler.