Here Kevin, I'll be nice and give you some help: Sidney has lived an effed up life since we last saw her in Scream 3, so much so that she kills herself. One year later, people start dying again. Is it the father who's finally snapped? Or is it her boyfriend, who's pissed at the world and what it did to her. Or... Is it Courtney Cox who's suffered from a turn of events over the last 10 years, many feeling her books causing their relationship to sour again to the point Courtney's cash-cow dried up to the point where maybe Sidney didn't kill herself at all... Maybe she was murdered, Courtney "stumbling" upon evidence a year later suggesting so that spurs a renewed interest, which of course, spurs more deaths.
The biggest problem is there haven't been any good slasher flicks in the last 10 or so years to riff on. Good luck Kevin...