While waiting on the outcome of an OPR investigation Mulder and Scully are assigned to the ISU. Mulder is forced to profile again.
According to Dawson's webpage: The question most often asked by first-time visitors to this page and this novel is, "What does ELS stand for?" It's an acronym. Saying more than that would spoil this novel beyond repair. So, you'll have to read to find out.
This fandom is so blessed to have writers of the calibre of Dawson E Rambo. This is another of his epic fics that meanders through a lot of angst and UST as they deal with their feelings towards each other and solve multiple cases.