Hi, I've been trying to find this game the past several hours. I played this game as a child, so it's a child game.
It's a detective, strategy, third person game. You're on a mission to find something/discover truth. You cannot use WASD keys, it's strictly point and click. I believe you can touch and examine objects by clicking on them with your mouse. I believe one of the scenes was you're outside, in the moonlight (the outside looks so wonderful, you can see the full moon, the dark blue night sky and stars). I believe you're outside a mansion and you click on the mansion to get inside. Another scene, you're outside again and you're beside a river, or a park with a river. It's still night time. The objective is to get items and mix them with the items in the inventory to get to different places.
I played this game as a child, so I believe the game was made in 1999-2005. I bought it in Kazakhstan, and I'm not sure whether it was in Russian or English (the text). Once again, it's a child game.
I was reminded of this game when I watched this video. One of the songs played in this video is one of the soundtracks that is played outside that mansion area that I've mentioned! You can skip to 0:10-0:25 part in the video.
https://www.youtube.com/watch?v=Tnu43KOADCQ
Whoever finds it, is incredible. My childhood thanks you.