Complex sentence: Buffy and Faith sneak into City Hall to try to find out what Finch was doing in the alleyway in the first place; although all of his papers have been shredded, they do learn that the Mayor is in league with Mr. Trick.
Split into simpler sentences: Buffy and Faith sneak into City Hall to try to find out what Finch was doing in the alleyway in the first place. They find that all of his papers have been shredded, and that the Mayor is in league with Mr. Trick.