Mr. Caine is one of the few reasons to sit through “Harry Brown,” an exercise in art-house exploitation directed by Daniel Barber and tarted up with self-importance and a generally striking visual design. Shot in digital and often at night — here, even the days look sunless, this being London at its least merry — it features an Expressionistic palette (bottomless blacks, sickly yellows, ominous reds) and steady, even stolid, camerawork and precise framing, which first complement Harry’s routinized life and then underscore his resolve. Every so often the camera starts jerking about as if the cameraman were suffering a seizure (the presumably fit cinematographer is Martin Ruhe), as in the frenzied scene that opens the movie with a drug-addled youth randomly killing a mother in front of her child.

Harry enters peeking from behind the curtains in his upstairs apartment, watching the world, or at least his little corner of it, go to hell, courtesy of a gang of young thugs. Unlike Leonard (David Bradley, a terrific character actor), his friend and chess partner, Harry initially believes that this bad element is best left to the police. Then Something Happens. Actually, a few things happen, which clears the path for Harry’s righteous wrath. Suffer the little children and all that, because without a few innocent victims, Harry might still be shuffling around his apartment. But with a wife in the hospital and a daughter in the ground, Harry takes on his new role without the usual pesky distractions, like a grasp of right and wrong.

Mr. Caine’s transformation from passive retiree to avenging marauder doesn’t work dramatically, but storytelling subtleties and character nuances are beside the point in a distraction of this type. The real and perhaps only point is to watch Mr. Caine play an old dude who mows down a lot of villains, which he does plausibly. He performs his nasty work with verve, not only because he’s fired a lot of movie guns, but also because he brings the memory of his great roles to every part. That’s especially important, given that this story sputters and drags as it tries to draw you into an uninteresting cat-and-mouse involving a gang leader (Ben Drew) and a detective (Emily Mortimer, miscast or just unmoored).

The most vivid scene, though, doesn’t belong to Mr. Caine but to another character actor, Sean Harris, who recently burned through the “Red Riding” trilogy playing a corrupt cop. He shows up here as Stretch, one of the story’s living dead. Harry enters Stretch’s spider hole, looking to buy a gun. What he finds is some pulpy nonsense — including a needle dangling out of the arm of a drooling, vomiting young woman — and a warehouse full of marijuana plants. Stretch seems as if he were into harder stuff (crystal meth and human sacrifice, from the looks of that pretty young thing). But there’s a wildness to Mr. Harris’s performance that goes beyond the artfully applied scars, a frenzy that suggests nothing short of real evil.