The agents pursue a serial killer who appears to be choosing his victims based on numerology.
Tropes of this episode:
Blonde, Brunette, Redhead: Agent Reyes finds out that there is a Serial Killer at large and that his pattern consists murdering women in a set of three. Each set has a blonde, a brunette and a redhead. Redheaded Agent Scully and dark-haired Reyes get trapped in an underground garage and fear they might be his next targets.
Breather Episode: The killer is played for drama but the rest of the episode is light and in fact, good natured especially compared to the rest of the grim Season 9.
God Was My Copilot: The ending implies that the mysterious man who shows up several times in the episode is God.
Numerological Motif: The whole episode deals with numerology and tries to show everything can be expressed in terms of numerological patterns.
Serial Killer: He targets women and kills them in a set of three.
Something Completely Different: The episode features, among other things, a comedic guest performance from Burt Reynolds and a bizarre musical number. Even Fox's bumper for this episode was something different from the usual "standing around and looking serious" business.