Sometimes, I just can't say it better than the press release, so here's a quote on the backstory of Secret Files: Tunguska
"It’s June, 1908. You are a Russian, doing normal Russian things northwest of Lake Baikal, in the middle of Siberia. As you and your comrades are... I don’t know, bolshevizing, maybe?... you see a large column of light as bright as the sun appear nearby. Then, a HUEG LIEK EKSBAWKS 'SPLOSION happens and knocks you on your back, where you sustain a massive and highly improbable head injury and die, thus removing you from this narrative. What happened? Well, you'll never know, 'cause you're dead. But other people will research this event for decades. Eventually, some will say that it was an air burst from a comet or meteoroid entering the atmosphere. But others say that it was something else. Something more... sinister."
Yep, that's word for word. It's coming to the DS and Wii at the end of the month.