There is something primally horrifying about the spindly alien tripod machines in Steven Spielberg’s new adaptation of H.G. Wells’s novel The War of the Worlds—they exploit the seemingly innate human fear of spiders, perhaps, or of anything insectoid and with the wrong number of legs articulated in a decidedly unmammalian way. They rivet the lizard brain, that unthinking, instinctive part of the human mind, gripping it in an irrational terror that has nothing to do with the insidious mission of the Martian creatures operating the vehicles. The beholder of such machines—whether that beholder is a character in the film or a moviegoer munching popcorn, or unable to, as the case may be with this flick—does not need to know what havoc the Martians are bent upon to appreciate that they are pure evil... or that they are at least utterly unattuned to our own monkey concerns.

Wells’s readers of 100-plus years ago would surely respond the same way to these visuals as we do today, were they somehow able to time travel to 2005 and check out the Spielberg flick—Wells makes a particular point of what trepidation the “monstrous beings of metal” induce. The aliens themselves, though, play less of a role in the new film than they do in the book, appearing significantly in only one scene without the protection of their tripod vehicles. But Wells’s descriptions resonate through Spielberg’s vision as well: these 21st-century Martians, like Wells’s nineteenth-century ones, are “unspeakably nasty.”

The downplaying of a particular unspeakableness of alien life in itself way well be partly an inevitable upshot of Spielberg’s own efforts (however unintentional those efforts may have been) toward making us less fearful of the concept: cuddly E.T. and the musician-philosophers of Close Encounters of the Third Kind are certainly the most prominent examples in pop culture of alien visitors as benign, kindly, and just here to make friends with us. Wells, on the other hand, was writing for a culture still reeling from the paradigm-shattering breakthrough of Darwinism and naturalistic biological evolution; his readers may indeed have found repulsive the idea of alternative lines of evolution in a way that we today do not—certainly Spielberg’s intended audience of SF fans and young people of persuasions geeky and otherwise have grown up with the concept of possible alien life and are perfectly comfortable with it (at least on a fictional level).

And indeed, what is frightening in Spielberg’s War is not alien life per se—instead, the most treacherous and creepy things about these new Martians is that they’ve been hiding among us, in a sense, plotting and scheming our destruction for millennia, or longer. This seemingly insignificant departure from Wells is actually quite profound, and serves to point out—along with many other smaller details Spielberg incorporates into his adaptation—how some signals of “scary” or “upsetting” are simply products of our environment. Wells’s readers in 1898, for instance, may have shared our unease with the gangly tripods, but they are unlikely to have been dismayed the way we today are by the image of Tom Cruise’s Ray Ferrier covered in ashy gray soot after the film’s initial attack by an alien tripod. It’s clear, in the film, how he comes to be so filthy—the Martian heat ray pulverizes its victims, reduces them to so much dust—but what’s really horrifying about the imagery is how it reminds us of 9/11: Ferrier after escaping the attack looks strikingly like the dazed, ash-coated survivors of the collapse of the World Trade Center. Our imaginary time-traveling Wellsian audience would have understood from context why Ferrier ends up such a mess, but they would not have understood why Spielberg chose to make such a point of it, and it would have had little visceral impact on them. (It’s unlikely, too, that they would have been quite so able to sympathize with Ferrier’s revulsion, once he realizes what’s all over his clothes and in his hair and on his face, in the same shuddery way that we do.)

Conversely, Spielberg—with his screenwriters, Josh Friedman and David Koepp—was wise to omit one especially unpleasant Martian weapon Wells deployed to potent effect in the novel: the Black Smoke. Wells, of course, was rather presciently anticipating the gas warfare to come only a few years later in World War I, and it’s probably not possible to know now whether there was something already in the cultural zeitgeist at the turn of the twentieth century that would have particularly rattled his readers in the idea of a deadly black fume... but there’s probably no question that the concept of gas warfare is so far removed from our experience now that such a thing would not have the psychological impact that, say, another Spielbergian appropriation from 9/11 does: bulletin boards tacked with hundreds of flyers seeking information on missing people, which is dramatic not for what it says about how many people are “missing” but for what it says about how the survivors are unable to admit to themselves yet that their loved ones are dead. That, again, brings a level of reality and recognition to Spielberg’s vision that makes it uniquely a product of the early twenty-first century, for all that it is in many ways a fairly faithful mounting of Wells’s story.

But that sneakily profound departure from Wells? It’s what gives Spielberg’s film a fundamental grounding into today’s culture-wide anxiety about terrorism and the apparently inability to distinguish friend from foe that’s been hammered into us by overly intrusive “security” measures that suggest that anyone, anywhere could be up to things devious and malicious. Wells, writing in a period in which jitters over German unification were creating an atmosphere of war fever—or war dread—invoked the specter of invasion from without, of The Other attacking what should be safe and secure Home. But in Spielberg’s War, the Martians have long since secreted their fighting machines among and around us—they’ve not only infiltrated us, they did so long before we, humans, were even around, and then just waited patiently for us to ripen—they are still Wells’s “intellects vast and cool and unsympathetic.” The film’s promotional tagline, “They’re already here,” is particularly chilling for us today, when threats of attack (whether real or imaginary) seem to be all around us, seem to loom not from faraway places but to well up from within our own society. Instead of science fiction, we’d could well consider this new War of the Worlds a horror film geared especially to the age of the Patriot Act, which warns us that the enemy is already here.