This documentary is about the Tunguska Incident and analyzes the possible causes of this huge mystery. Some synopses I've read say this is about alien theories, but the movie is more about scientific well known theories and the alien possibility is very briefly brought in.
What makes this film standout is that at some point the producers realized they had just a bunch of footage of boring science professors talking to the camera and decided to make things more fun by adding a host, which is a fat man in a spaceship talking to a sentient computer that has an evil robot voice! This host segments are just there so we don't fall asleep. The guy starts as some wise investigator but he becomes more and more weird and lunatic as the movie progresses.
In the final third through the movie they run out of Tunguska material and the documentary switches to a completely unrelated recapitulation of the space race!
And when you are near the ending and wondering, what the hell I am watching? Out of nowhere is a final very cheesy scene of aliens (which are just women in Egyptian costumes) coming from space and destroying Earth. Oh, so that explains the title?