June 27 issue - When you're making a $135 million movie about aliens invading Earth, it's good to have some rules. So in 2003, while Steven Spielberg was shooting "The Terminal" in Montreal, screenwriter David Koepp flew north with a list of cliches that he believed "War of the Worlds" had to avoid. "Here are the things we could not have in this movie," Koepp says. "One: no destruction of famous landmarks. Two: no unnecessary beating up of New York City. Three: no politicians or scientists or generals as main characters. Four: no shots of military leaders pushing ships around on a big map with sticks. And five: no shots of world capitals." If they'd been able to peek into the future, they might have added six: no star who's going to have a Howard Dean moment on "Oprah," and turn prerelease publicity into a referendum on his love life.

The good news is that the debate over Tom Cruise—who last week proposed to Katie Holmes atop the Eiffel Tower—will seem far less pressing once audiences get a look at the massive, terrifying spectacle that Spielberg has created in "War of the Worlds." "Every time Steven embarks on a genre movie, he reinvents the genre," says producer Kathleen Kennedy. "He never wants to be derivative." She laughs. "If he ever gets derivative, he's only derivative of himself." "War of the Worlds" marks a return to the crowd-pleasing fare that made Spielberg the most successful director in history: think "Close Encounters of the Third Kind" with a far more sinister edge. There are images here—the wreckage of an airplane, an alien tripod rising to full height behind a ferryboat, a river of corpses, the clothes of the dead floating down through trees like snow—that are just breathtaking. And, OK, Cruise is pretty great.

Based on the 1898 science-fiction novel by H. G. Wells—the first alien-invasion story ever written—"War of the Worlds" isn't really a battle between planets. It's more like the annihilation of ours. Cruise plays Ray Ferrier, a divorced, blue-collar guy more interested in fast cars than in his young daughter (Dakota Fanning) and teenage son (Justin Chatwin). But then huge alien tripods begin destroying everything in their path, and Ray finds himself on the run with his kids. "Tom's played so many characters that are capable and cocky, and I thought it would be fun to write against that," says Koepp. "Ray is someone whose life didn't pan out the way he thought it would, and who became kind of a jerk as a result." (Cruise himself declined to be interviewed for this story.)

While details have been changed from Wells's novel, the fear at the core of it remains intact. In 1938, Orson Welles's radio adaptation seemed so real that people famously wept in terror and fled their homes. Even the now campy 1953 movie, produced by George Pal, frightened audiences at the time. "There's always been something in the air before this title has reared its ugly head," Spielberg says. "They were all times when the world was heading to an uncertain future. Wells's book was a political statement about the invasion of British colonialism. Orson Welles did his radio show several years before America was drawn into World War II. The Pal movie came out during the cold war, when we were afraid of being annihilated by nuclear weapons. And this movie, my version, comes out in the shadow of 9/11." As the aliens launch the first wave of destruction, Fanning, 11, screams, "Is it the terrorists?"

If it irritates some critics that, as in Wells's novel, Spielberg's movie never explains why the aliens feel the need to incinerate man-kind, the director says it's all about amping up the tension. "Having no idea why they're killing hundreds of thousands of people is scarier than having them arrive, make an announcement and then go to work," he says. Koepp, in any case, has a private theory. "I think the whole war is about water," he says. "I figure their planet ran out. Wars tend to be fought over very elemental things: water, land, oil."

Despite the epic scale of the film, Cruise gets to skip (most of) the heroics, and play a man just barely holding it together. In one scene, Ray and his daughter hide in a basement that belongs to a crazed survivalist (Tim Robbins). Terrified, the girl asks her dad to sing her a lullaby, and he realizes that he doesn't know any. Cruise looks heartbroken. "Every director's dream is when an actor stops thinking and starts living," Spielberg says. "Tom did that in one take. Something very real happened in that moment. He sort of gave it up, and probably didn't even know what he was giving up until it was too late and I said, 'Cut'."

Which is not to say that Cruise never gets the chance to be a stud. When NEWSWEEK visited the set in February, a shirtless Cruise was strapped into a stunt harness for the film's climax. The harness suspended him, face down, high above the concrete floor. "I don't like my actors doing stunts," said Spielberg, holding an unlit cigar. "I did five takes with the stuntman, but then Tom came in and saw that I was shooting a scene without him and immediately put on the harness." He shrugs. "If the stuntman deems it safe, I'm OK with it. I have a real tough time stopping Tom Cruise." It's amazing that anyone, from any planet, still tries.