Christopher Landon's "Happy Death Day" was one of the nicer surprises of 2017, an unabashed rip-off of "Groundhog Day" and "Scream" in which a college girl, Theresa "Tree" Gelbman, must relive the day of her murder until she kills the killer. It shouldn't have worked, but the movie wisely downplayed the blood and cranked up the YA appeal, focusing on its youthful cast, romantic subplot and dorky sense of humor. Horror movies are rarely endearing; this one went so far as to include cute, animated end credits.
The sequel, "Happy Death Day 2U," offers diminished returns, but it's not completely unrewarding. Plotting, pacing and logic are weak points, and the source material _ this time it's "Back to the Future" _ seems like a less inspired theft. The good news, though, is that the original movie's strengths are all here as well.
They include Jessica Rothe, of television's "Gossip Girl," who gives Tree a late-'90s, post-Gellar aura _ blond hair, delicate features, eyes brimming with emotion. Carter, the calm yin to Tree's chaotic yang, is played once again by a likable Israel Broussard. Phi Vu returns as Ryan, a minor character now elevated to the role of catalyst: It's his lab project on quantum mechanics, a pulsating machine named SISSY (after the endless rock-roller Sisyphus), that caused Tree's initial time-loop.