Grade: 2.5/5.0

No story comes as sequel-ready as time travel shenanigans. “Happy Death Day” had a lot of fun smashing a slasher whodunit into its adopted “Groundhog Day” premise. Sorority girl Tree (Jessica Rothe) was tasked with sifting through her social Darwinist caricature of Greek life to track down her killer, with her inevitable murder always sending her back to the beginning of her day. Doubling down on the delightful bargain-bin kitsch of its predecessor’s title, “Happy Death Day 2U” comes bundled with the enticing prospect of returning to this closed loop to dig deeper into its peripheries.

Picking up a day after the original ended, “Happy Death Day 2U” opens with Ryan Phan (Phi Vu), the geeky dorm mate of Tree’s boyfriend Carter (Israel Broussard), heading to the not-at-all conspicuously titled Quantum Lab on campus to check on his thesis project. There, he finds a masked killer that stabs him and sends him back to the start of the day.

After Tree relates her experience with the phenomenon, Ryan drags all the characters to the lab and realizes his science experiment is the cause of the time loop. A freak accident activates the machine and sends Tree back to the day she escaped in the original. She is forced to crawl out of the same hell she’s already lived through countless times.

These first 20 minutes or so following Ryan threaten to employ a shopworn approach to sequels that are usually misguided — handing off the story to minor comic relief. While this opening is amusing enough, it ends up proving how integral Rothe’s performance is to making this “live-die-repeat” repetition sing.

The actress finds numerous shades to her character’s ever-evolving Stockholm syndrome, deftly balanced between charm and crabbiness. Staid exasperation gives way to manic screams whenever she accomplishes a task as if cheering after beating a difficult level of a video game. By the final showdown, no twist can catch her off guard, and she’s loading a handgun with the mechanical assurance of Schwarzenegger in his heyday.

If there’s any justification for doing the time warp again, it’s the heavy-lifting Rothe accomplishes as the lead; navigating such a tricky tone so nimbly is an impressive feat and certainly proves more entertaining than almost every performance currently nominated for an Academy Award. The fact that she’s mildly less dazzling this time around comes down to matters outside of her purview. Firstly, any shock of the new is gone. But, more specifically, the indecisiveness of the script saddles her with a grab bag of insipid dramatic stakes that suck the carnival trick morbidity out of the series’ central existential gag.

Surprisingly, “Happy Death Day 2U” is very rarely a slasher movie, and the few moments it tries to be mostly play as obligations to the original. Instead, it’s more of a loose comedy, riffing on different forms of familiar pop confection — a couple fragments of a family drama here and there, a heist movie for a tick, a big-hearted romance during the climax. The problem is, the movie has no clue how to combine these things, playing each piece out in a vacuum.

These forced contortions, which were done in an attempt to appear interesting, betray the elegant simplicity that gave the original its narrative propulsion. The only element inherited wholesale is the winking camp, less wittily deployed here and a downright overbearing force at times. In a cowardly move, the B-movie frivolity is utilized to temper the inherent absurdity of the concept, as opposed to enhancing it. The movie seems hell-bent on hand-holding its audience by mocking its own laborious sci-fi trappings or trafficking in rote parent-child drama as some paltry gesture toward sentimentality.

Whether it’s a conscious refusal to take itself seriously or sheer ineptitudes on the part of director Christopher Landon, the ostentatious tackiness of “Happy Death Day 2U” is what ultimately holds it back. The film peaks with a montage of Tree’s various suicides accompanied by the hysterical selection of “Hard Times” by Paramore (at the very least, the movie knows its audience). It’s easily Rothe’s best showcase, carried by gallows humor and giddy plasticity that would make Wile E. Coyote blush.

But the film almost never goes for broke, sticking to facile gags like a slow-motion explosion ironically set to classical music. Rothe is fully equipped to handle the cornball romp “Happy Death Day 2U” tries to be, but nothing matches her level of commitment.