CONTAINS SOME SPOILERS
Of all the recent horrors that might have engendered a sequel, Happy Death Day probably wouldn't have been high on the list. It was a decent enough comedy slasher with a Groundhog Day twist: a girl found herself living her eighteenth birthday over and over for no apparent reason, getting repeatedly murdered by a masked maniac again and again until she found the killer, bested them in the final reel and finally made it to Tuesday. And this followup initially appears to be following the exact same path: the sequel that's actually a remake - until it reveals its hand early on and suddenly leaps without any warning into head-spinning SF territory concerning quantum physics, alternate dimensions, parallel realities and a few moments that actually approach poignancy. And barring a few missteps, it's terrific.
Maybe it helped that I knew nothing about Happy Death Day 2U going in and didn't even rewatch the first one as revision; happily that didn't matter as I got up to speed very quickly. This time it appears to centre around science nerd Ryan, so minor a character from the first movie (eleventh billed) that I'd forgotten about him entirely, who finds himself in the same old time loop when the baby-masked killer leaps out of a cupboard at him. But his roommate's girlfriend is Tree, the oddly-named heroine of the first movie who immediately figures out what's going on, ties it up with Ryan's theoretical physics experiment and ends up repeating her death day again in a parallel dimension where everything isn't quite the same - can she survive her daily comedy suicides long enough to figure out a way back to her own world?
It's very smart, it's very funny (I laughed out loud in the cinema which is practically unheard of these last few years), and it's constantly throwing ingenious twists into proceedings and moving quickly enough to jump over any plot problems. I did wince a little when someone namedropped Back To The Future Part 2 and Inception, partly because it always annoys me when films try and justify borrowing an idea by mentioning it in dialogue so they can pass it off as affectionate homage (and neither reference is strictly accurate anyway). The main misstep comes with an unnecessary comedy heist sequence where they have to break into the Principal's office and they have to stage the most idiotic diversion that tips the film into knockabout farce. It doesn't work and it doesn't need to be there and seems to exist simply to give those actors their moment in the light. That aside (plus a needlessly cruel mid-credits stinger), it's a lot of fun, pushing the boundaries of modern disposable slasher cinema into much more interesting areas and mostly keeping it under control. Probably unlikely to make the Top Ten of the year, but it's entertaining throughout and way better than we had any right to expect. Strongly recommended.