Trivia: As Frank is running up the stairs in the FBI, just before he meets Peter you can see "Mulder and Scully" walking down the stair case - this is in fact David Duchovny and Gillian Anderson's stand-ins, but they do look a lot like them.
Kingdom Come - S1-E6
Other mistake: At the start of chapter 12 in the episode "Kingdom Come," Frank returns home via taxi. In front of his house in Seattle, WA, there is a blonde woman walking a Rottweiler dog. This same blonde and Rottweiler can be seen walking by the crime scene in San Francisco in the "Gehenna" episode.
Jordan Black: Will we always be together?
Frank Black: Of course.
Jordan Black: Forever?
Frank Black: Well, nobody gets forever.