Nowhere in this scenario will you find justifications for the overall plan. There may be explanations of specific events. I may even let little parts of the plot go. On the whole, though, there are going to be several things happening and various characters/creatures appearing for which there is absolutely no explanation. Consider this my attempt to try to get the feel of alien logic and overarching conspiracies across.
This scenario typically is distributed as a ZIP archive containing several documents:
10-page RTF scenario
4-page background notes
Two 1-page RTF print-and-play pre-generated characters
Four 2-page RTF print-and-play pre-generated characters