This is not the greatest episode in the world and the story is rather convoluted and fields weirdly somewhat far-fetched even for an X-Files episode. I don't know whether it's in the writing or the direction, but it just felt a little 'clunky' alongside other better ones. That being said, it is still pretty good with a fair share of chills and gore. The premise is around a series of murders of four people, a similar set of murders that has been happening on certain dates in the past. The deaths of one set of victims correspond with the births of others etc.
The method of murder is skinning alive and the special effects team really comes into its own here. The body is very believable - though less so to me was how someone could remove the skin and leave all the arteries and veins intact without an incredible amount of skill. There is a particularly unsettling scene in an abattoir, which is already place with dead carcasses in it.
It does tell us more about Monica and her abilities - actually it's a shame these weren't further exploited, but that would have probably taken another series of the X Files. The ending and the culprit are a little easy to guess.
So I wouldn't call it a classic, but it's still worth a look.