Does evil fall into the world like a rock from outer space? Does it spring from within us? Or is it merely the residue of our blunders–our trespasses, literally–which we commit while coping with circumstance? These are large questions for a comic-book movie to raise, especially when it’s the sequel to a sequel. But whatever faults I can uncover in Spider-Man 3 (just give me a minute), lack of ambition isn’t one of them.

Not content to end this trilogy by having the superhero fight a bad guy, or even three, director and co-writer Sam Raimi has given Spider-Man the grandest possible send-off by making him struggle against evil itself. If you have not yet bought your ticket, please be advised that the outcome will not be conclusive. Don’t even expect coherence. Like a CGI-crazed billionaire reshooting the funhouse scene in The Lady From Shanghai, Raimi has addressed his subject by multiplying and mirroring and fragmenting it, so that representative evils crash and splinter around a hero who never locates the definitive source of the threat. All that can be said for sure is that the proposed sources of evil, in aggregate, seem comprehensive, and that one of them may be discovered in the hero’s own moral failings.

As we know from the earlier films, young, mutated Peter Parker was always apt to be self-involved and vengeful. Now, in Spider-Man 3, these faults begin to dominate his personality. Peter grows infatuated with celebrity, pursues a personal vendetta and ignores the feelings of his beloved Mary Jane. The result is further mutation, as he changes into jerk Peter, floppy-haired Peter, Peter with a ladies’ man swagger and a sense of entitlement. You may judge the nature of the transformation by its critical site: a men’s discount clothing store. But if personal emotion should seem too weak a cause for the existence of evil, Spider-Man 3 offers a more elaborate explanation, in which Peter is a victim of malevolent goo from a meteorite. In this scheme–alternative to the first as an idea but simultaneous with it on the screen–Peter’s worst traits would have been nothing more than weaknesses, had they not left him vulnerable to an alien intruder: some black, bloblike stuff, with a texture that’s reminiscent of a fetishist’s vinyl.

Despite its kinky sci-fi trappings, this is the metaphysical evil of old-time religion: an uncanny force beyond our power to comprehend, which may mimic its victim (as the space goo sometimes imitates a spider’s scurrying) but comes from outside him. The opportunistic blob has a will of its own, and like Satan goes to and fro in the earth, walking up and down in it. Here again, mutation occurs and reveals its nature by its critical site: a church steeple.

The third major site of mutation–yes, there’s still another, the most impressive of all–looks like a huge concrete mixing bowl, overhung by a glowing electronic eggbeater. The sign posted on the fence outside claims this apparatus is an experimental physics station; but it’s more like the place where bad luck, poverty and common ignorance get stirred into a threat to society. A poor brute named Flint Marko stumbles into this installation, wearing the most baffled expression that Thomas Haden Church can give him, and an outfit apparently copied from a 1930s French movie about the poetry of the lower depths. Marko enters the mixing bowl as an escaped convict, already presumed to be a danger to the public. He exits as a shape-shifting mass of sand: an invisible man, ground down by a world he doesn’t understand, but newly capable of living outside the law.

I write these words and hear the groans and chortles of incredulity. Can a mere corporate product like Spider-Man 3 be so layered with psychology, sociology and religious conviction? Of course it can–if you’ll admit that the man charged with spending two years and a gazillion dollars on it might have thought about what he was doing. No one who watches without prejudice this extravaganza of doppelgängers, moral preaching and existential dread will complain that it’s mindless. On the contrary: My complaint is that Raimi has loaded too many big ideas into Spider-Man 3. They drag this bag of kittens right down to the river’s bottom.

The heaviness of the production is visible all too plainly at a vulnerable point, where Tobey Maguire’s jawline is now softening into a jowl. I know, I don’t look so great myself–but then, I’m not supposed to be a college student endowed with miraculous athletic gifts. With every close-up that Raimi takes of Maguire, especially those from a low angle, you’re reminded that the Spider-Man series itself has aged, and like Peter can’t pretend to have much ingenuousness to lose. Every once in a while, Raimi still manages a flash of the first movie’s youthful charm: in a view of a parade reviewing stand, for example, where Cub Scouts seated in the front row blithely pass the time by kicking their legs. Just like Cub Scouts, you think. But quirky, naturalistic details like this one have now been almost abandoned, along with the first movie’s bracing sense of New York’s neighborhoods. A touristic view of Times Square passes for local color. The film’s “downtown jazz club” is a storefront restaurant with a dance floor and singing waitresses. Not even in Portland–though the worst part of this scene isn’t the bogus setting but the tortured editing that’s required to make Maguire look like he’s dancing.

Forced humor, forced fun, a forced sense of reminiscence (the movie’s so thick with long-established motifs, you’d think it was Spider-Dämmerung): These traits, combined with the grandiose theme, at last give you the impression not of ambition itself but of a desperate striving to be ambitious. It’s the difference between creating an ingenious, delightful action sequence and telling the audience you’ve created one; between having Peter/Spider-Man race through well-defined streets so he can deliver a stack of pizzas (as in the beginning of Spider-Man 2) and having him whip through a random jumble of city views so he can stop and pose before a screen-filling American flag.

Note the operation of the First Law of Movie Dynamics: As self-importance rises, concern for common sense falls. Those unfamiliar with this principle might imagine that a writer-director’s attention will be concentrated everywhere when greatness is the goal–that someone who so beautifully realizes the scene of Flint Marko’s transformation into Sandman (a wonder of characterization and feeling, not just of special effects) will maintain the standard he’s set. But see how the plot of Spider-Man 3 jerks along over groundwork that was incompletely laid. Convenient butlers dodder forward to supply information the characters ought to have known years ago. Unlikely changes of heart seize Peter, and then are magically undone a reel later, just so a conflict can be advanced. These breaks in the storytelling are too severe to be excused as mere shortcuts, taken for the sake of economy; but they are also too careless to be enjoyed for their own sake, as you might luxuriate in the incongruities of a more dreamlike picture. Here, you just get bumped out of the movie, for no better reason than that Raimi couldn’t be bothered to keep you in. He’s got higher priorities: preparing a long, loud battle for the climax, and writing some lines of fortune-cookie wisdom–repent! forgive! brush after meals!–meant to justify the clanging.

If forgiveness is the main concern of Spider-Man 3, then Raimi certainly has mine. He’s given me so much pleasure over the years (For Love of the Game notwithstanding) that I probably should be apologizing to him, for finding fault. But then, Raimi headed me off by working his own criticisms into the movie.

Through his affection for some of the supporting characters–a secondary love interest played by Bryce Dallas Howard, an evil twin to Peter (mostly comic) played by Topher Grace–Raimi implicitly disavows Peter and Mary Jane, who no longer seem to inspire him. You can feel his relief whenever he turns momentarily from Maguire and Kirsten Dunst (good as they are) to the new faces in the cast. As for the film’s outstanding performance, it’s surely given by that handsome mug James Franco, in the role of Peter’s sometime friend and sometime enemy Harry. There’s an airy freedom in the way Franco veers from obsessive rage to open-faced sweetness, from murderous scheming to heroic self-abnegation. Lucky him. He gets to play, while Maguire and Dunst are stuck discharging an obligation.

She never gets to relax in the movie, except in Franco’s company. He never gets to enjoy being a bad guy–even in that jazz club scene–but acts out his evil under compulsion. These are two seriously clenched characters–and the strain you sense in them tells you something about the explicit self-criticism in Spider-Man 3. Raimi’s story proposes that Spider-Man has now become too popular for his own good. The cheering crowds, the marching bands, the breathlessly impressed young beauties, the giant-screen video billboards: These ceaseless accolades weigh on Peter’s soul, the film tells us, and sadden Mary Jane.

It takes little imagination to conclude that the success burdening the characters now drags on the series, too. Impute the problem to social injustice, individual moral frailty or an ambitious extraterrestrial blob, but Spider-Man 3 is a come-down.