Pifias

While driving on a snow-covered road, Mulder collides with a truck equipped with a snow plow. His car's front headlight is visibly damaged. In the next scenes, the damage changes from shot to shot.

When Scully is on the phone with Agent Mosley, the computer in the background plays the exact same sequence twice in a row (a file downloading).

After Dacyshyn pushes Fox's car over, the underside shows a dual exhaust. Later when Scully calls Fox, the car again has a single muffler. In no shot does the car have a dual exhaust, including when it is pushed off the road.

When Mulder's car is attacked by the snow plow, the drivers window is shattered, when the car is pushed over the hill, the window is intact. The window is not intact. After it is shattered, in the next shots it is gone (due to being broken), and in a coupe shots pieces of glass are visible (the lack of visible broken glass in some of the shots can easily be explained due to the shots being too far away and the glass falling away as the car fell).

When Scully is talking to Father Joe in the hospital after his cancer diagnosis, a shot from behind the Father's shoulder shows his head raised off the pillow. When the shot changes, his head is lying flat on his pillow.

The first time Scully and Mulder accompany Father Joe to the scene of the agent's abduction, the sun is rising and the screen reads "Somerset, West Virginia, 5:02 AM". During mid-winter in that part of the country, it would still be completely dark at that hour.

Scully and Mulder fly in on a helicopter from their house. The rotor is still turning after they land and exit the helicopter, but Scully's and Mulder's hair remain in place. In the next shot, they are walking away from the helicopter with the rotor still turning. The rotor wash would blow their hair around.

While Father Joesph is hospital, the heart monitoring equipment on him is placed incorrectly. The black lead should be on his left shoulder, not green as seen in the movie.

Scully tells Mulder the FBI's toxicology report on the severed arm showed traces of a drug called acepromazine, which she says is unusual and should not be found in a human because it is an animal tranquilizer. While Acepromazine is mainly used to sedate animals prior to painful procedures like suturing, or to help calm them down prior to being put under anesthesia, it is also still used in humans on rare occasions. Acepromazine was first developed in the 1950's and was one of the first antipsychotic medications, though it fell out of frequent use when more effective antipsychotics like chlorpromazine (which is a closely related analog of acepromazine) were developed shortly after; its use in humans declined even further after the development of atypical antipsychotics like clozapine in the 1970's, which were more effective and much safer. However acepromazine is still available for human use, though its use is rare, it typically is only used in humans that do not respond well to modern atypical antipsychotics or have an allergy to them.

The drug Acepromazine is used in veterinary medicine as a muscle relaxer and stress reducer prior to general anaesthesia. It does not produce narcosis as seen in this film, this would require it being combined with another drug (eg Methadone) but this was not found on the bodies.

When Mulder is following the pick up truck to the hide out he scrolls through his phone contacts and highlights what some viewers have claimed is the name 'Gillian', the first name of Gillian Anderson who plays Scully. However, it actually says 'Gilligan', a tribute to Expediente X (1993) writer-producer Vince Gilligan (see trivia).

At 1m 33s the search party appear to be searching for something buried in the snow. They are all just lightly tapping the surface with the sticks, which will reveal nothing.

The helicopters used throughout are Aerospatiale/Eurocopter AS355 Ecureil 2, however the audio on the opening search & rescue is of Bell 205/212 (Huey). Later on the FBI helipad, audio of Bell 206 Jet Ranger is used.

In parts of the movie, you can clearly see snow capped mountains in the background. No such mountains exist in West Virginia.

In West Virginia, a sign for "United Petroleum Products Inc." appears. That is a strictly Canadian company.

Though the attacks occur in Somerset, West Virginia, in one scene shot from inside the victim's car, you can clearly see a Virginia State Police Inspection sticker.

In the film, they refer to the Richmond "DA" who appears later. Virginia has no District Attorneys; prosecutors are Commonwealth's Attorneys.

When Dacyshyn and the surgeon speak Russian, they switch between the familiar you (ty) and formal you (vy). Russians would never do that.