The Quest One Mo Time said that I needed to find the Cavern of Whispers in the Shinobi Cave (Khotan Skyway - MooShu). I found that you had to defeat at least one group of Inoshishi Bandits before you entered the Shinobi Cave to start the Quest Whispers in the Dark. Defeating Inoshishi Bandits is not mentioned in the Quest Journal and, If you avoid the Inoshishsi Bandits (it is possible – I did it by using the center of the circle the Bandits are moving around) and enter the Shinobi Cave, you cannot advance any further. It just says that you need to find the Cavern of Whispers in the Cavern of Whispers. The Quest Arrow points to the correct cave entrance in the Shinobi Cave (no door) but, when you go through it, the Quest Arrow points in the other direction. When you are at the exact entrance of the Cavern of Whispers, the Quest Arrow disappears without the game doing anything else. There was no mention of the Shadow Door.