- All Hallow's Eve series by Windsinger
- Messenger, The by Windsinger
Driving back to Washington on Halloween evening Mulder and Scully see strange lights in the sky over rural Maryland, stop to investigate, and find themselves spending a night they will not soon forget.
This one started out fairly painlessly, but Sue pushed the angst up each year as she added a new volume and sucked us in further. But wait, there's more! There's also a shorter story called "The Messenger" that works as an epilogue which I'll post separately as it fits into a few of the different universes that Windsinger was writing at the time. (There's a Cliff's notes guide to all the series involved at the end of that fic so you can follow it without having to read every story. )