Probably the most important of all the early episodes of the X-Files. Yes, even more than "Ice" (although thats a slightly better show, for me personally). Firsty, it establishes that the show is not just going to be about aliens and conspiracys. And what a way to show it!!! I read that they had a really hard time making this episode because of problems with the director, but it really doesnt show at all. "Tooms" is a scary character, mainly because of the way in which he gets to his victims. No one is safe, no matter how secure you are locked away. Its certainly not perfect. Scullys Mulder hating former colleagues are very annoying, although they are really only potrayed this way to make Scully's decision to side with Mulder easier to believe. But everything else is just great. The lie detector scene, the ending with Tooms in his cell.... scary.
The best thing is that he's brought back later in the season. Probably the best compliment you could pay this episode is by finding a random casual viewer and asking them to name an Xfiles villian.. and the chances are Tooms's name is the one that will come up