Complex sentence: Scully tries to contact her with no success, and receives a package soon afterwards containing a book about Native American beliefs, which describes how one man will be able to hold off the apocalypse and become humanity's savior.
Split into simpler sentences: Scully tries to contact her with no success, and soon receives a package afterwards which contains a book on Native American beliefs. The book describes how one man will be able to hold off the impending apocalypse and become humanity's savior.