The teenagers go to a Stab movie marathon at an abandoned old barn - tipped to be the final act massacre. Gale Weathers disguises herself in a Ghostface mask and places 4 cameras around the barn. She returns to her car to watch the CCTV footage - but someone starts to block each camera in turn (and pretty quickly too - they must be faster than Usain Bolt).
Gale returns to the barn - while Dewey shows up outside. He watches the CCTV as his wife holds the camera in her hand, and Dewey can do nothing as the killer appears behind her. Gale fights him off as Dewey races into the barn and shouts for the kids to leave. He tries to shoot the killer but misses a fairly easy shot three or 4 times, while the killer stabs Gale in the chest and gets away.
Sidney is at her Aunt's house, and is spooked by wind chimes outside. The cops outside are murdered - Seth from the OC is stabbed while the funnier black dude gets a knife in the head (!) but still manages to get up, walk around and talk some more. She gets a call warning her that something will happen to her family - so she races up to Jill's room but finds that it is empty, with Jill having left to go to Kirby's.
Sidney's Aunt returns home - and the 2 killers show up at each door. They shut them out, but the aunt is stabbed through the letterbox and dies. The female cop shows up, and Sidney manages to get out.
There's an after-show party at Kirby's house. Trevor shows up, claiming he was invited, and goes upstaits with Jill. The film geek with the camera, Robbie, gets drunk outside - and is soon stabbed. He tells the killer that he is gay - but it doesn't work.
Kirby and the fat film geek, Charlie, almost get it on until they are interrupted by Trevor. Sidney shows up - and they soon find Robbie covered in blood on the porch - followed by the killer. Sidney and Jill run upstairs. Sidney gets her cousin to hide under the bed as she climbs out the window and then gets away.
Sidney decides to return back inside, finds Kirby and together they get to the cellar. Sidney is brave and goes it alone back upstairs. Outside, Charlie is stuck to a chair as the killer plays a game like in the earlier movies. Charlie's mouth is frantically moving under the duct tape. She seems to get the answer right, so she goes outside to free him - but then Charlie pulls out a knife and stabs her.
Back in the kitchen, Charlie and the 6ft manly and very strong killer confront Sidney - and the mask is removed to reveal the face of Jill. I know, like in Scream 2 with the middle aged lady it makes no sense. All those people who have been murdered should be disappointed with themselves to have been chased and scared by a chubby, 5ft-small dorky kid and a thin girl with issues.
Jill stabs Sidney and goes on about how she hates her and has been envious of her fame as a survivor. The killers shoot Trevor in the groin and then through the head, hoping to frame him. Then, like in Scream 1, the killers have a pact, but Jill kills Charlie (who has feelings for her as well it seems) to claim all the fame, and starts to beat herself up (so she'll look better for the cameras as it's not needed to frame Trevor even more than needed as all the dead bodies lying around the place pretty much point to a murderer at the party) by running into things and tearing out her hair.
In hospital Jill is woken up by Dewey, who lets on that Sidney is alive. Jill is understandably upset by this. Dewey doesn't notice and goes to see Gale - but then figures it all out when he says that Jill asked about Gale's chest wound when that crime report wasn't released. Of course the fact that all the teenagers at the party saw it and 95% of victims were stabbed in the chest by the killer(s) over the 4 movies would make someone hedge their bets that they knew what went on.
Jill gets into Sidney's unguarded ICU room, and starts to beat her up again. Dewey arrives, and is knocked unconscious by a bedpan. Gale and the female cop show up. Jill has dewey's gun and tells the cop to drop hers - which for some unknown reason she does, and is shot. As Gale keeps Jill distracted, Sidney fries her cousin's brains with the paddles.
Dewey wakes up. The cop also gets to her feet and shows off a bullet-proof vest. Somehow Jill is not dead from the 4000volts to her head, so Sidney turns and shoots her.
Outside TV cameras show reporters with different views on the events, but most claiming that Jill was the victim and Trevor the real killer.