Another variant on "Freaky Friday," this time riffing on Freaky Friday the 13th. Kathryn Newton is Millie Kessler, a pretty but somewhat shy and bullied teen. When a mass murderer (Vince Vaughn) stabs her with a magical dagger, they swap bodies overnight. So Vaughn spends most of the movie acting like a teen girl in the body of a very tall middle-aged man, and Newton acts like a murderous psychopath trapped in the body of a fairly small teen. Despite looking like "The Blissfield Butcher," Millie manages to convince her best friends (Celeste O'Connor and Misha Osheovich) that it's actually her - so the three of them run around town trying to undo the body swap - as our young and pretty Butcher makes short work of some of the school's nastier teens (seriously - that's not a plot spoiler, you got all of it from the trailer and the rest from every previous slasher comedy).
Vaughn turns in a game performance as a teen girl, but has previously been outclassed by Jack Black in both the Jumanji movies. In Vaughn's defense, Black couldn't have done as good a psycho killer, but Black does the better young woman. Newton was reasonably good as a middle-aged psycho. The comedy was passable, but I found a lot of the structure too rote: I correctly guessed the first kill, and while I didn't get the order on the rest I had a pretty good idea who would fall. And of course there was also a looks-dead-but-isn't-actually resurrection toward the end of the film. Too formulaic, and not quite funny enough to justify that.