Grade: B

This film from William Friedkin (“The Exorcist”) is being marketed as a conventional horror movie, which is absurd. Though it certainly has its share of horrific moments—more so, in fact, than run-of-the-mill Hollywood shockers—Tracy Letts’s adaptation of his 2004 off-Broadway play is basically a brutal portrayal of paranoia. The film to which it might most properly be compared is David Cronenberg’s “Spider.” But while that picture was far subtler, portraying the deranged mind from within, as it were, and doing so with an almost unparalleled form of cinematic severity, this one is a view of paranoia from the outside, told in a furious and florid style. And though not the equal of Cronenberg’s film, it’s an intriguing and powerful alternative to it.

There’s more than a hint of Sam Shepard in the set-up, milieu and undercurrents in the movie. Agnes White (Ashley Judd) is a waitress living in a dismal motel room in the Oklahoma boonies, and bothered by repeated telephone calls in which no one speaks when she answers. Eventually it becomes clear that she’s afraid they’re coming from Jerry Goss (Harry Connick, Jr.), her ex-husband just out of jail and a threatening sort of fellow. It’s also eventually revealed that their troubled history together includes the loss of their young son, who unaccountably disappeared during a shopping trip with his mother. And Jerry himself eventually turns up at the motel.

Before he does, however, others have entered the scene. One is R.C. (Lynn Collins), Agnes’s lesbian friend, and along with her Peter Evans (Michael Shannon), a strange, oft-spoken young man she’s met at the bar. Agnes and Peter quickly develop a quiet rapport, and she offers to let him stay the night. Gradually a halting romance between them emerges, though his curiously controlled mien and the occasional hint he lets drop about his fears suggest that all is not as placid within him as it might be.

As the piece moves into what’s clearly its second act, the susceptible Agnes has been fully drawn into Peter’s extreme paranoia, expressed in his belief that as a soldier in Iraq he was the subject of experimentation that involved the injection of some tiny bugs under his skin (presumably to control and/or track him), and the pair lock themselves inside the room against the dangerous world outside. Their already paralyzing fear is only increased when a government doctor (Brian F. O’Byrne) shows up seeking Peter. The condition in which he finds them, and their reaction to his intrusion, are not pretty.

To appreciate “Bug” you have to be willing to immerse yourself in somebody else’s fever dream, and especially in its final stages, it’s not a pleasant experience, although it is drenched in—among other things, some of them very red—a streak of mordant humor. Though not pleasant, however, it’s certainly compelling. The only issue is how many viewers might care to be compelled in this way.

It’s also marked by two extraordinarily strong performances. Judd, after years of starring in lousy action-heroine movies, recently reminded us, with her subtly understated turn in “Come Early Morning,” that she’s a fine actress, and here she’s ferocious and courageous, refusing to hold anything back. And Shannon, who played Peter on stage in the original production, is a revelation, anchoring the film with a turn that captures the oddity and obsessive drive of the character without ever stumbling into mere caricature. The claustrophobically close-in camerawork of Michael Grady doesn’t flatter them in the Hollywood sense, but it captures the frantic movement that accentuates Friedkin’s vision as well as the intensity of lead characters’ view of the world. The supporting cast delivers soundly, with Connick working up a fine sense of menace and O’Byrne one of almost nonchalant bemusement in the face of the outrageousness he sees around him.

From the simple narrative perspective, there are questions implicit in “Bug.” For example, was that lost child that destroyed Agnes and Jerry’s life real, or imaginary (as in “Who’s Afraid of Virginia Woolf”)? But the big one, of course, is whether Peter and Agnes really have little critters crawling around inside them. Probably not—but though the characters in it might not actually have bugs under their skin, Friedkin’s creepy film will certainly get under yours, for good or ill.

To speak nautically, the first “Pirates of the Caribbean” movie, “The Curse of the Black Pearl,” was a surprisingly spiffy vessel for something cobbled together from an amusement park ride, buoyed by Johnny Depp’s engagingly droll performance as the rogue Jack Sparrow. By contrast the sequel, “Dead Man’s Chest,” was a creaky, worm-eaten thing, encrusted with narrative barnacles and weighed down by the dutiful quality of Depp’s repeat turn.

The downward spiral continues with the third installment, “At World’s End,” a sunken, moribund wreck of a movie housing no treasures whatever. It will doubtless repeat the inexplicable boxoffice success of its predecessor—testimony to the lemming-like proclivity of today’s audiences not only to rush to even the worst retreads but in some cases to do so repeatedly. But it’s a convoluted, ponderous, joyless spectacle whose lack of charm is matched only by its incoherence. Why Gore Verbinski would have chosen to follow the goofy wildness of the first picture and the overstuffed slapstick of the second with such a puffed-up (an unconscionable 167 minutes), plodding, largely poker-faced finale is hard to fathom; it seems he’s now taking this franchise much too seriously. What’s clear is that though the movie’s final joke has to do with agelessness, the series itself is at death’s door.

The studio has asked critics not to reveal details of the plot in their reviews—a request that’s easy to accede to, since the picture’s story arc is pretty much incomprehensible. It basically has to do with the evil Lord Beckett’s (Tom Hollander) plan to sweep piracy from the Caribbean to protect the interests of his West India Company, now with the connivance of tentacle-faced Davy Jones (Bill Nighy), who’s in his thrall, and the Flying Dutchman. (The movie begins with a really peculiar sequence in which Beckett is seen summarily executing everybody with connections to the pirates, including a sad-faced child—suspending all civil rights in the process. This may be intended as a critical allusion to current U.S. policy against modern “terrorists,” and if so the makers can only hope most American viewers won’t notice and take umbrage.)

On the other side are the recently resuscitated Captain Barbossa (Geoffrey Rush) and the romantically linked team of Elizabeth and Will (Keira Knightley and Orlando Bloom), who make their way—via a stratagem that involves Singapore pirate chief Sao Feng (Chow Yun-Fat)—to Jones’ Locker to retrieve the deceased Jack Sparrow (Depp) and then bring all the pirate bands together in a coalition against Beckett. Also involved are an assortment of supporting characters, including a sea goddess called Calypso, the voodoo enchantress Tia Dalma (Naomie Harris), Will’s father Bootstrap Bill (Stellan Skarsgard) who’s a member of Jones’s enslaved and mutated crew, Sparrow’s aide-de-camp Gibbs (Kevin R. McNally), Elizabeth’s old beau Commodore Norrington (Jack Davenport), several sets of comic-relief players (most notably Lee Arenberg and Mackenzie Cook as the bedraggled Pintel and Ragetti), a monkey, and a slew of other pirate captains, one of them Teague, who turns out to be Sparrow’s father and, as played by Keith Richards, is about as simian as the real thing.

The ways in which all these characters—and a small army of additional ones—deal with one another consist of treachery piled upon duplicity. Each person has his or her own secretive agenda, and joins with foes or turns on allies for reasons it would take Brainiac to decipher and keep track of. At one point a character inquires of Sparrow, “Do you think he plans it all out, or just makes it up as he goes along?” One might ask the same question not only about him, but also of scripters Ted Elliott and Terry Rossio and every character they’ve created.

But however the writers work, the result is a mishmash, a jumbled chain of crosses that aren’t just double and triple but quadruple and quintuple. The puzzle might be fun to play if it wound up anywhere interesting, but it doesn’t. And the journey there is mostly glum and sluggish—not to mention overly gruesome and violent for the younger set. To be sure, the cinematography is sumptuous, if often dark—there are some lovely shots during the trip to Davy Jones’s Locker through arctic wastes and under star-filled skies, for example, and a couple of surrealistic sequences involving multiple Sparrows are visually imaginative, even if they’re oddly humorless (a problem with the entire picture) and would be more appropriate in a film that might be nominated for a foreign-language Oscar than this one. But for the most part the effects are curiously unimpressive this time around, and the score by Hans Zimmer that accompanies them the sheerest bombast.

As to the actors, they’re trapped on a sinking vessel. Depp shows a few moments of his erstwhile zest, but he’s mostly repeating old tricks, an even paler shadow of his turn in “Curse” than in “Chest.” (It doesn’t help that Elliott and Rossio haven’t supplied him with many witty lines.) Watching Bloom and Knightley go through their paces, one might wonder whether a more colorless pair of lovebirds have ever graced the screen. And Rush mugs and rasps his way through a part that’s just a standard-issue pirate caricature, parrot and all. The rest are just wasted—including Nighy, still encased in his heavy Jones makeup, and Chow, who’s dispatched after just a few dreary scenes. At least Hollander can content himself with a ludicrously overblown farewell moment (in slow-motion that seems positively De Palma-esque), although for most of the movie he’s required to exhibit nothing beyond pursed lips and a gentleman’s sneer. And then there’s that little monkey, which serves the same function here that cute little pooches do in many movies, in a plethora of reaction shots that are supposed to make us smile. By the fifth or sixth appearance they’ll probably make you grimace instead.

And then, for some reason, there are crabs—hundreds, thousands of them (all CGI, of course)—appearing in two big effects sequences. Why Verbinski is drawn to them is anybody’s guess. But their presence is oddly appropriate: sitting through this big, overblown, gloomy end to the “Pirates” trilogy is likely to make you feel very crabby indeed.