Though it’s nothing more than a brainless action thriller that grows increasingly preposterous as it proceeds to a ludicrous conclusion, “The Accountant” raises one troubling concern about contemporary storytelling—the treatment of autism, or of its cousin Asperger syndrome. The documentaries on the subject—even uplifting ones like “Life, Animated”—are serious, mostly sober affairs, and fiction films that employed it as a plot device generally treated it with extreme sensitivity (think, for instance, of “Adam,” “Rain Man,” “I Am Sam” or “What’s Eating Gilbert Grape?”). That emphasis was clear even in a thriller like “Mercury Rising.”

Now, however, such a condition is increasingly being used, rather crudely, as a convenient plot device. “The Darkness” was a dreadful horror movie, but one of its most contemptible aspects was the suggestion that autistic children were somehow closer to the forces of darkness than anyone else, and could unleash malignant spirits into the world. Now Bill Dubuque’s script implies that such a child is especially suited for training as a cold-blooded killer—a skill that can be combined with his super-human aptitude in some intellectual activity (like mathematics). Such depictions are becoming sadly common in contemporary pictures, a screenwriting crutch that would be better avoided.

If one can set that aside, however, “The Accountant” can serve, especially for its first hour, as a guilty pleasure.

After an enigmatic prologue about a mysterious killing spree in a run-down area of NYC, the film introduces Christian Wolff (Ben Affleck), a small-town CPA in an Illinois strip mall advising a farming couple (Ron Prather and Susan Williams) about how to avoid bankruptcy. He’s a rigid, laconic fellow who has trouble interacting with people, and flashbacks explain his personality. As a boy (Seth Lee), he was diagnosed with a disorder that gave him special aptitude in completing puzzles (for example), but made him excitable and unable to socialize. Rather than putting him in the care of specialists, his father (Robert C. Treveiler), a hard-nosed military man, trained him and his younger brother (Jake Presley) in martial arts, believing that tough love would enable him to live an independent life.

Affleck, it should be noted, is just about perfect for the role. He’s always been an inexpressive actor with a stiff demeanor, who might remind you of the cruel comment that Pauline Kael once made about Laurence Harvey: that he finally found a role he was capable of playing convincingly in “The Manchurian Candidate”—that of a “brainwashed zombie.” Here Affleck adds a few tics and obligatory daily rituals to fill out the portrait of an intensely self-contained man struggling to live a “normal,” if solitary, life.

But it turns out that Wolff is much more than a simple small-town CPA. The film switches to the Treasury Department in Washington, where Raymond King (J.K. Simmons), an aging agent on the verge of retirement (naturally), blackmails young analyst Marybeth Medina (Cynthia Addai-Robinson) to identify the strange young man who’s glimpsed in the background of photos with some of the world’s most nefarious figures, acting as a “forensic accountant” to determine when they’re being scammed. I’s obviously Wolff, though it takes a good deal of investigation for Medina to reach that conclusion.

Meanwhile Wolff is hired by Lamar Black (John Lithgow), founder of Living Robotics, and his sister (Jean Smart) to locate the source of the siphoning off or company funds that’s been discovered by one of their young accountants, Dana Cummings (Anna Kendrick). He does so, but soon he and Dana are being stalked by a ruthless hit-man (Jon Bernthal) and his cutthroat gang. Meanwhile King and Medina are on Wolff’s trail.

“The Accountant” begins with a puzzle motif, and that’s how the movie is structured, with the pursuit of Wolff and Cummings by the hit-men juxtaposed with Wolff’s tracking of them, and the identity of the person who hired the hit-men part of the mix. All of that is accompanied by flashbacks to Wolff’s past and the dogged work of the Treasury agents, which itself is marked by a major series of revelations, including one focused on Francis Silverberg (Jeffrey Tambor), a master mob accountant turned government informant. Everything eventually adds up, in a purely narrative sense, but hardly in a way that anyone could call credible or even remotely plausible. And a final confrontation not only comes across as a compendium of every action-movie cliché one can imagine, but closes with a twist that (like the identity of the chief villain) is not only discernible far in advance, but so utterly coincidental that even one of the characters has to remark on how unlikely it is.

The essential absurdity of the film doesn’t stop it from being entertaining at a rudimentary level, particularly in the first of its two hours, but it does make one wince at the thought that the script is constructed so as to allow for a sequel—or even a series of them. Nonetheless the picture is enlivened by O’Connor’s energetic direction, and by the performances—not just Affleck’s but Kendrick’s (though she has little to do but be pixie-ish), as well as those of the always reliable Simmons, Tambor and Lithgow. Addai-Robinson and Bernthal make strong impressions as well, even if they’re playing cardboard figures. Technically the movie is a solid job, well designed (by Keith Cunningham—the corporate boardroom, with glass surfaces suitable for mathematical computations, is especially attractive), and with editing (by Richard Pearson) that keeps the plot strands reasonably clear. Seamus McGarvey’s cinematography is generally very good, though the action sequences aren’t always ideally crisp, while Mark Isham’s score is okay but forgettable.

Apart from its treatment of autism as a plot ploy in the service of pulpy fiction, there’s not much to think about after watching “The Accountant.” But if the movie doesn’t entirely add up, it can provide some dumb fun along the way.