Mulder's behavior suddenly becomes erratic, his actions evasive as he forces Scully away from a case that's been given to him under mysterious circumstances. And eventually Fox Mulder is faced with the decision of a lifetime.
This is a hard-to-find story from Writergal2000; a mytharc fic set in season 6 with throwbacks to the DAT tape in Anasazi. There's a bit of unrest between the partners, as Scully gets fed up with Mulder's attempts to protect her. Things work out of course.