The Tunguska event was a large explosion that occurred in Russia, thought to be caused by a meteor even though no impact crater was found. The story of Secret Files is based on this mystery. I'd imagine the game is inspired by Broken Sword, whose story tied into history and conspiracy theories. It's probably the reason why there is two playable protagonists in the game; Nina and Max.
Nina Kalenkov goes to the Museum to meet her Father that works there. However, his office is ransacked and he is missing. She meets Max in the adjacent office, then with the help of a former colleague, Oleg; they then go on a journey that spans many countries.
The game is a point-and-click adventure, and often you have many items in your inventory. You often grab items without a purpose, then work out what you need them for later. There are some objects that are useless, so you pick them up, but never need to use them. There's quite a lot of puzzles that require you to combine items in your inventory. You can press the Space Bar, or an in-game button to highlight areas of interest, then it's a case of right-clicking to hear information, or left-clicking to pick up if appropriate.
There were some bizarre puzzles throughout the game but I solved them quickly; especially the ones in the first half of the game. For example, when you have to eavesdrop a conversation, and so you have to use a cat to be your “fly on the wall”. I think the reason I solved the bizarre puzzles was the fact that you pick up items in an area and there's a limited amount of objects in the scene to interact with. If my items contain food, phone and tape, and there's a cat next to a feeding bowl and near a cat flap; and my overall objective is to listen to a conversation; then it's a solution that is crazy enough to work.
Sometimes I solved puzzles that I didn't even know I needed to do. It didn't seem that clear that you had to get rid of the two scientists on the train. One of the scientists was doing an experiment at his desk, and I blew the fuse of a machine he wasn't even using. That made him leave the room to find a replacement fuse. It was just a case of me having a particular item that I didn't know where I needed to use it, but there was an object I hadn't interacted with yet, so I tested it out.
There's a few problems with the voice acting, where sometimes it seems to be delivered with the wrong tone, and Nina often starts insulting or patronising people she was supposed to be sweet-talking. There's a lot of dialogue that is written as if they get interrupted by someone else, but it doesn't sound convincing with the delivery, and sometimes there is a noticeable pause for the next person to speak. Nina's constant use of “Daddy” was a bit annoying. It's not usually a word adults would call their Father.
I think Nina and Max are supposed to be Russian and German respectively, but both talk with strong American accents. I thought this made the chapter where Nina breaks into a heavily guarded Train station a bit silly. She dresses up so would look like a new recruit, but speaking English in a strong American accent is a bit of a giveaway. I guess the language is for the benefit of the player, but the fact that they don't have the appropriate accents is a strange choice.
The story isn't well paced. The initial set-up is great, but then there's parts where the story doesn't really progress, then the final moments deliver a somewhat rushed conclusion. It's decent enough but has its flaws. I found myself enjoying the game less as the game progressed.