The X-Files: Dark Matter is a novella written by Easton Royce. It was first published in 1998.
Description[]
A man disappears, leaving nothing but his shadow burned into the floor. And he's not alone; there are two other "missing" people in the same town. Special Agent Fox Mulder suspects a bizarre string of spontaneous human combustions -- until he stumbles upon the shadow of a much darker force at work...