Call it scream therapy for tweens and teens.

"Twilight" heartthrob Robert Pattinson, ensconced in a car on his way to a King of Prussia mall, was about to be smacked with another wave of fan adoration and hysteria.

Asked what was happening outside Philadelphia, he laughed and said by cell phone, "I'm not entirely sure. Uh, I guess another screaming session. I've kind of been going from city to city. I go to a mall, get screamed at and then go to the next city."

Fans come with roses, tattoos, tears, telltale T-shirts ("Team Edward," "Your scent is like a drug to me" and "Bite me," among others) and rapid heartbeats as they near Pattinson, who plays drop-dead gorgeous vampire Edward Cullen in the movie opening today.

In San Francisco, eyewitnesses called it pandemonium. Philadelphia reported hysteria. In Boston, girls wept with anticipation, a reporter duly noted. A Canadian Press account said admirers in Toronto "swooned, shrieked and professed their devotion."

As for Pattinson, he has never been as devoted or obsessed about anything as the readers of the "Twilight" books are. They've bought 17 million copies of "Twilight" and its three follow-up books and launched 350-plus fan sites.

"I find it completely fascinating, how you can actually get to that level. People aren't even coming to watch a show or anything. They're just there to see someone walk by for one second. I mean, it's crazy." But crazy good.

Pattinson, speaking for everyone connected with the movie, says, "I really hope it all translates," and advance ticket sales indicate fans anticipate that it has. Sales are as brisk as they have been for an established film franchise, such as Bond or Batman or Harry Potter.

In fact, until recently, the 22-year-old British actor had been known for playing Cedric Diggory in "Harry Potter and the Goblet of Fire" and "Harry Potter and the Order of the Phoenix."

Now, he's a beautiful boy with perfect, ultra-white teeth, a velvet voice and an intoxicating presence. That's how human teenager Bella Swan, played by Kristen Stewart on screen, describes Edward in the Stephenie Meyer novel. Writers, meanwhile, have gone to great lengths to describe his full lips, generous eyebrows and swooping, signature hair.

"When I did 'Harry Potter,' I'd gone into it when it was already a fully running machine," he said.

"There had already been three movies made and then I did this, and it was very much in the embryonic stages, I mean everyone scrambling to figure out how to make this into a basis for a franchise and no one really knew what it was at the time we first started. So, I guess it was different, it was a very different energy."

When director Catherine Hardwicke was shooting "Twilight," seven or eight fans might show up nearby.

"I kind of expected that. It's a cult book. ... And then, suddenly at the end of the shoot, on the last day of re-shoots in L.A., about 150 people turned up. You suddenly realize, 'Oh, OK, now I'm beginning to understand what this is,' and then Comic-Con happened. I think if we were shooting in Portland again now, there'd be tons of people the whole time."

Ah, yes, Comic-Con. At the San Diego fanfest, teenage girls and some of their moms delivered the shrieks heard 'round the movie world.

"That was really the first time that I ever realized the extent of people's obsession with it. Now it's happened quite a few times all around the world. I'm kind of getting a bit more used to it. That time at Comic-Con was absolutely baffling. I really, really wasn't expecting it."

Asked how faithful the film is to the book, he says it would be pointless to simply duplicate the 498-page book (not to mention ridiculously long). Although "tons of stuff" is missing, Pattinson says the movie captures its essence, core and tone and may even surprise filmgoers.

"Twilight" may be about a vampire who falls for a teenage girl in the cloudy, rain-soaked town of Forks, Wash., but it carries some universal themes.

In the book, Edward tells Bella, "Just because we've been ... dealt a certain hand ... it doesn't mean that we can't choose to rise above -- to conquer the boundaries of a destiny that none of us wanted."

Pattinson elaborates, "A lot of the story has to do with not obeying your base instincts and having your humanity win over what is essentially the beast, in you, and I guess what you can achieve with your own self-control. That you can really overcome anything and also whether it's worth doing that, whether it's the right thing to do, that's kind of what the story's about."

Hardwicke comes to "Twilight" after directing "The Nativity Story," "Lords of Dogtown" and "Thirteen." As eclectic a group of movies as you may ever find, but all dealing with teens.

"I guess a lot of people who make movies like the darker side of life and they like things to be very mixed emotions, but Catherine is very good at having a very uncynical, unironic view of just things like love, pure love."

In fact, while he and Stewart wanted to emphasize the difficulties of their relationship -- vampire and human, hunter and hunted -- Hardwicke "wanted to emphasize the sort of transcendent nature of what they have between them, so it ends up being a compromise between the two. I mean, it's not entirely one thing or the other with Edward and Bella's relationship."

Living inside Edward's pale skin was invigorating in one regard.

"When I was shooting it, it was interesting to see that he definitely has this confident aura. Obviously, anyone who's living forever has an air of confidence about him," because he doesn't care what the rest of humanity thinks.

That quiet confidence seeped into Pattinson's real life. "Immediately after I finished it, I immediately became a frantic, nervous person."

And that was before the screams even started.