Goofs

The tin of matches by the fireplace of Tooms' second victim changes position between shots.

There is a close up shot of Scully's cut phone lines, showing her in apartment #405. When Mulder kicks open the door to her apartment, the number on the door is 35.

When Tooms' grabs Scully's leg, his arm is completely out, yet in the next shot of him it's further inside again.

When Scully is having lunch with her friend just after the intro, we see at one shot from behind her she is holding a knife, then when the shot changes she is no longer holding it.

When Mulder is comparing Tooms' fingerprint to the one found in Usher's office and stretches the current one like the older one, they are exactly the same. This would be extremely unlikely since the angle and amount of pressure would have to be identical.

Detective Frank Briggs tells Mulder and Skully that he had been waiting 25 years for someone to question him about the case. If the killer strikes every 30 years, why would the detective have been waiting for only 25 years?

The reason that he states that he has been waiting 25 years for them to come speak with him is because he was a police officer for 5 years after the last murders. Once he retired he knew that in 25 years (because the last murder was 5 years before he retired) the murderer would strike again and then the investigating officers would be coming to speak to him because of the matching MO's in both the cases.

After Tooms is handcuffed to Scully's bathtub, you can see the edges of his colored contacts in a closeup.

Prior to attacking his first victim, Tooms enters the office through a vent that's screwed in place after unscrewing its screws from inside the vent. But this would be impossible since the screws would be inside the wall and he wouldn't be able to grasp them.

The murders being investigated are in Baltimore, yet the episode opens with a victim walking past the sign for Oceanic Plaza in Vancouver.

There are no mountains with 150 miles of Baltimore Maryland.

Scully, an FBI agent, hints that another agent stopping or hindering Mulder from the investigation could be seen as him "threatening another officer in the commission of his job."

FBI sworn law enforcement always refer to themselves as "agents" and they insist that others do the same. Scully would never refer to a fellow agent as an "officer"; nor would the other agent as it would be demeaning.

The characters are mispronouncing "Powhaten", pronouncing it 'po-haten', when actually it is the 'h' that is silent, not the 'w'. It should be pronounced 'pow-aten'.

Mulder wears glasses when he first starts scrolling through the microfiche to find out about Tooms; but later scenes don't show him wearing them. Since he doesn't wear them for driving, we are led to believe they are for reading, but he doesn't use them more than once.