"I Am Legend" has a distinct drop-off point, which is a shame, because for an hour it's a surprisingly absorbing last-man-on-Earth movie. Why surprising? Because the director, Francis Lawrence, made "Constantine," which was two hours of visual noise. This one actually takes its time, creating some sights worth the gape, though they tend to be rather simple and unshowy sights, such as Will Smith stalking the empty, weed-strewn streets of Manhattan, looking for something to eat.

Working from a script by Mark Protosevich and revised by Akiva Goldsman, the new film is the third big-screen adaptation to date of the 1954 Richard Matheson novella. Smith stars as Dr. Robert Neville, apparent sole survivor of a viral plague, the result of a cancer cure gone horribly wrong. The film begins with news footage of the doctor responsible for the miracle, played by Emma Thompson, acknowledging her contributions on camera. Something in Thompson's wily eyes suggests a flickering doubt or two regarding the cure's efficacy. If you ever see this same look in your own doctor's eyes, switch doctors.

Matheson's story rides on a very simple and flexible premise, which is why filmmakers keep returning to it, changing particulars depending on the times. Our own time has fixed post-9/11 Manhattan as an epicenter of horror-hence the New York setting. For a long time, profitably, "I Am Legend" chronicles the daily routine of Neville as he and his dog search for food, the primary order of business. A few stray computer-generated deer have survived the plague, along with the odd computer-generated lion. Plus, Neville has "the dark seekers" to mess with: These are the vampiric denizens of the night, part human but transformed by the plague into bloodthirsty devils. Their closest cinematic cousins are the well-dressed bloodsuckers in the recent "30 Days of Night," to name one film less entertaining than this one.

Holiday audiences will be expecting something grander, more gleefully destructive, and "I Am Legend" refuses to satisfy such expectations. There aren't many big surprises here; suffice it to say that Neville is not alone human-wise, and his discovery is roughly where the film starts sputtering en route to a conclusion that feels like a studio-sanctioned reshoot. Still, you're willing to cut the movie a break; for most of the way it's starker (even with the comic relief) and more eerie in its atmospherics than the usual big-budget monster. Then again, I liked "The Mist," which did not do well at the box office-although that film's unhappiest-ending-ever ending didn't help much crowd-wise.

A true artifact of its time, the last big-studio remake of Matheson's story was "The Omega Man" (1971), which featured Charlton Heston swaggering his way around the ghostly sunny streets of post-apocalypse L.A. In that film, one of the red-eyed monk-robed adversaries allergic to daylight mocked Heston as a hollow man living in "honky paradise," behind homemade barricades, while the streets ran rampant with undesirables. (The evil ones were led by Anthony Zerbe, however, who was nothing if not a honky, in addition to being a good actor.). With the Smith remake of "I Am Legend," the racial lines have been reversed. It's genial but determined Smith against what's left of the world.

Contemporary film audiences are unpredictable about what sort of futuristic depictions of earthly hell they'll support. For years this remake was in development as an Arnold Schwarzenegger vehicle, its backers surely hoping for some of that "Terminator 2" box office magic. I suspect such magic may elude the film that came to pass. But Smith carries it, even after the story loses its nerve. This film is the opposite of "Transformers": It's all about the unsettling silence, not the noise.