The story of M. Night Shyamalan’s career is certainly a dramatic one, encompassing massive hits like “The Sixth Sense” and catastrophic failures like “After Earth.” Heading into one of his films, it’s never quite clear whether it’ll be a success or a truly memorable disaster. But fortunately (for both Shyamalan and audiences), “Glass”—the third in a superhero-themed trilogy that began with 2000’s “Unbreakable” and continued in 2016’s stealth sequel “Split”—is mostly the former, even if its ambitions sometimes exceed its grasp.

On the streets of Philadelphia, David Dunn (Bruce Willis) moonlights as the poncho-clad “Overseer,” endowed with superhuman strength and dedicated to vigilante justice. A battle with the “Horde” (James McAvoy)—the psychologically damaged serial killer Kevin Crumb, harboring 24 separate personalities vying for control—results in Dunn’s incarceration in a psychiatric hospital, under the watchful eye of Dr. Ellie Staple (Sarah Paulsen). As it turns out, the hospital also happens to hold the enigmatic Mr. Glass (Samuel L. Jackson), a brilliant mastermind responsible for dozens of deaths.

Dr. Staple has a very specific project in mind: curing Dunn, Crumb, and Glass of their delusions of superhero grandeur. She’s determined to convince Dunn and Crumb that they don’t actually possess superhuman strength, and that Glass isn’t preternaturally brilliant. In her view, these delusions all stem from early-life traumas, which have left Dunn, Crumb, and Glass permanently scarred. It’s all in their heads.

Like much of Shyamalan’s films, “Glass” is a remarkably slow-burning thriller. There’s very little violence or intense action throughout its two-hour runtime. In fact, most of the dialogue in the film’s first hour comes from Dr. Staple, whose soothing voice and reasoned explanations almost lead us to believe she’s onto something—that the whole trilogy really is a sordid amalgamation of delusions and traumas.

It soon becomes clear that her character is strikingly reminiscent of another: the Lady of the Green Kirtle, the antagonist in the fourth installment of C.S. Lewis’ Chronicles of Narnia, “The Silver Chair.” In that book’s climactic scene, the Lady attempts to convince the novel’s heroes that all their values and all their efforts are purely illusory—that the only reality that exists is her cold, silent, underground kingdom.

“You have seen lamps, and so you imagined a bigger and better lamp and called it the sun. You’ve seen cats, and now you want a bigger and better cat, and it’s to be called a lion. Well, ’tis a pretty make-believe, though, to say truth, it would suit you all better if you were younger. And look how you can put nothing into your make-believe without copying it from the real world, this world of mine, which is the only world.”

In so doing, Dr. Staple reveals the film’s fascinating and unexpected thematic core: “Glass” is a defense of metanarrative over against its contemporary critics. That is, the film’s players are part of a single, larger story that cannot be reduced to chance or coincidence: there is an origin, a pattern and a terminus. This story stands apart from any one person; individuals may choose to acknowledge it or not. Dr. Staple’s overriding goal is to convince her charges that no such metanarratives exist—to persuade them that there are no “higher stories” other than those we tell ourselves. Dunn, Crumb, and Glass can certain formulate personal narratives of their actions and their place in the world, but these narratives must be understood as strictly therapeutic devices. In her account, “what is truth?” must become “what is your truth?”

“Glass” is a double-barreled demolition of this paradigm. In this film’s universe, comic books and superhero narratives take on a quasi-theological function, (seemingly serving as stand-ins for sacred texts). Written off by most of the world as pure fantasy, comics actually reflect primordial truths about superhuman beings and their interactions with the world. This is the “twist”—well, maybe not the twist, but a twist—at the center of “Glass”: there really is a transcendent narrative unfolding at all times, and a transcendent order that governs the world.

At bottom, “Glass” is the thematic opposite of “Deadpool” and “Watchmen”: where those films relied on a postmodern dismantling of classic superhero tropes, “Glass” is a post-postmodern reconstruction of the genre in an already-jaded age. It is, in short, anti-ironic. And that makes it a genuinely original and fascinating movie to watch.

From a cinematic standpoint, “Glass” is mostly effective—the claustrophobic setting of the psychiatric hospital makes a wonderful staging area—but periodically fumbles in the pacing department. The climax arrives rather too abruptly, and the final moments of the film feel a bit too cheery for this series. Additionally, Anya Taylor-Joy’s Casey—the heroine of “Split”—doesn’t have much to do here other than utter some inspiring phrases about human compassion. After her bravura performance last time around, it’s a shame she’s so upstaged by Dunn and company.

But on the whole, these are minor gripes. “Glass” is the superhero movie I’ve wanted Hollywood to make for almost a decade—a dark, heavily theme-driven tale that eschews heavy CGI in favor of memorable storytelling. As far as I’m concerned, the old Shyamalan is back, and the multiplex is better for it.