Like the mathematical variable itself, the X-Men, the oppressed, super-powered mutants from Marvel Comics, can stand for almost anything. Outsider groups especially: minorities, gays, misunderstood geniuses, megalomaniacs, science-fiction fans, and, of course, teenagers. In 1999, Bryan Singer’s X-Men, the first film adaptation of the 40-year-old pulp franchise, expertly courted everyone’s inner teenager, a creature chastened perhaps by the Columbine massacre earlier that year but still turned on by the notion of puberty as the onset of such alienating but quasi-divine characteristics as telekinesis or 18-inch stilettos thrusting between one’s knuckles.

For nearly half of X2: X-Men United, whose title evokes such disparate elements as spy planes, Irish activist pop groups, and English football icons, Singer’s knack for anticipating and acting out current events and anxieties prevails, as does his talent for turning the overwhelming visuals of an f/x-heavy fantasy into a witty, ironic, and poetic mise-en-scène. For about an hour, in fact, before it gets lost in its own evolutionary dead ends, X2 might be the most subversive film of the summer.

Which is quite a surprise when you consider that Twentieth Century Fox is allied with Fox News. The images of helicopters full of US Special Forces descending into the night are eerily familiar after the saturation broadcast coverage of Operation Iraqi Freedom. They aren’t rescuing Private Jessica this time, though — they’re attacking Professor Xavier (Patrick Stewart) and his School for Gifted Children, the wheelchair-bound mentor’s base of operations for training young mutants to co-exist with normal humans. I imagine the loyalties of most viewers are going to be tested when Wolverine (Hugh Jackman), he of the 18-inch stiletto blades, skewers his first camie-clad commando. Aren’t those guys supposed to be on our side?

Not all is as it seems in this war on terror, however, such as the foiled opening assault on the president by the Teutonic teleporter Nightcrawler (Alan Cumming looking like a Satanic chimney sweep in blackface and with a pointed tail). It might have been set up by Magneto (Ian McKellen), Xavier’s alter ego, an all-powerful mutant capable of mentally manipulating metal and dedicated to wiping out humanity. Except that the mutant-hating Stryker (Brian Cox), a shadowy, Cheney-like government operative, has imprisoned Magneto, Hannibal Lecter–style, in a plastic prison. Perhaps Stryker himself is behind the attempted assassination, with the idea of forcing passage of the film’s version of the Patriot Act, "The Anti-Mutant Registration Act."

All this is, up to a point, told with clarity, panache, and provocative insinuation. Unfortunately, Singer feels obliged to include more and more material from the comic book’s four decades of shifting characters, plots, origins, and conflicts. As long as he inserts the references slyly — say, a glimpse of Colossus here or Dr. Hank McCoy there, enough to get a knowing nod from X-Men aficionados — the material adds a zesty density. When he pursues these digressions doggedly, however, the film evolves in unproductive directions. Unlike a 135-minute movie, a comic book, which is published monthly over many years, mutates toward no particular goal other than to avoid losing reader interest.

X2 loses sight of its goal at the most crucial point. A grudging alliance forms between Xavier’s X-Men and Magneto and his sidekick, the sexy, shape-shifting Mystique (Rebecca Romijn-Stamos, who deserves a movie of her own), as they lay siege to Stryker in his undisclosed location underneath a dam in the frozen north. The big showdown, however, sputters into one dam thing after another, with about four different and equally confusing parallel narratives taking place, each highlighted by handsome if pointless action sequences (a battle between Wolverine and his female counterpart would like to be a classic). In addition, numerous characters confront their various neuroses and screwed-up relationships — Rogue (Anna Paquin) and Iceman (Shawn Ashmore), now there’s a dysfunctional couple — and it all gets a little silly. "This is one lovers’ quarrel we don’t want to get involved in," quips Magneto to Mystique as Cyclops (James Marsden) sends heavy equipment flying with blasts from his eyes in an assault on his girlfriend, Jean Grey (Famke Janssen). Too bad Singer didn’t take his advice.