It's called "Spider-Man: No Way Home" but a better title for this exhausting sequel would be "Spider-Man: For Superfans Only."

There are a lot of prerequisites for "No Way Home," which wants you to have seen and have excellent recall of all previous "Spider-Man" movies (including, briefly, the best one, "Into the Spider-Verse").

Spoilers are already out there but I won't reveal who pops up. Just be ready for characters/actors you haven't considered in a while, in-jokes with very long tails and plot lines you thought were wrapped up long ago. It would also help if you can remember how the Spidey suit has changed from film to film.

"No Way Home" benefits from the return of Zendaya as M.J., girlfriend of Peter Parker/Spidey (Tom Holland). Her ironic sense of humor and deft underplaying are huge assets, which is why it's too bad she disappears for large portions of the new movie. Holland is fine, if a bit bland (and his big emotional scene, while well acted, is very poorly written). But Zendaya should be the superhero here.

It's also nice to have a sizable role for Benedict Cumberbatch's short-tempered Dr. Strange, on board to offer a segue to his starring movie next year and to help Spider-Man tackle a batch of villains who materialize from the multiverse.

Basically, parallel universes collide in "No Way Home," which sometimes slides into the do-I-need-a-physics-degree-to-understand-this territory of "Interstellar," but Strange and Spidey are trying to put things right again.

Unfortunately, there are so many moving parts in "No Way Home" that it becomes bloated and chaotic. It suffers from Marvelitis, that condition in which movies are 45 minutes longer than they should be.

There are about five endings. And the movie can't decide how it feels about its supervillains. An intriguing idea is offered — it's possible they need help, not killing — but that gets muddied during the multiple endings.

The post-credits sequences drop hints that the multiverse will become central to Marvel movies — the Dr. Strange sequel is actually called "Dr. Strange in the Multiverse of Madness" — and I hope that's not bad news. "No Way Home" already treads on that slippery slope where if everything is possible, maybe nothing really matters.

That's worrisome. I suspect I won't be the only viewer who, after finishing "No Way Home," will remember Dr. Strange saying, "The multiverse is a concept about which we know frighteningly little," and think, "Doc, you said a mouthful."

Spider-Man: No Way Home

⋆⋆ out of 4 stars

Rated: PG-13 for violence and language.

Where: Area theaters.