I came up with this first at IMDb and thought it was pretty good, hahaha, naturally!
It takes place in a mental institution, let's say, Woodsboro Home for the Bewildered.
There are 2 ideas:
1) Sid is the patient or,
2) Sid is the psychologist.
If Sid is the patient, this can lead to her doubting if she really belongs there, and she really does sound crazy, but she's got a suspicious-seeming boyfriend/husband (again) who convinces her it's for the best, a doctor who thinks she needs more time in therapy (also suspicious). Dewey and Gale visit her one fine Sunday, when the place loses power. All over town. Dewey and Gale help Sid escape because the security's down, etc. And the killing begins anew...
If Sid is the doctor, this can lead to her suspecting a new patient of being homicidal. Another patient (a creep of course) has the hots for her and so does a fellow colleague. There is no end to Sid's admirers. In fact, she is a guest of honor at a homicidal maniac doctor's convention and must give a speech. The place is crawling with doctors. Or so we think. One of them is also a patient. Not so oddly, Halloween rolls around, Sid decides to go out with colleagues from the hospital to escape obnoxious teenagers in ghostface costumes. And the killing begins anew...