Elemental enough and not completely elementary, I Am Legend is sci-fi for the masses. Hollywood's third major screen version of Richard Matheson's 1954 novel -- after The Last Man on Earth starring Vincent Price in 1964 and 1971's The Omega Man with Charlton Heston -- may boil down to a zombie flick with a religious motif, yet it entertains the way a popcorn movie should.

Think Cast Away meets 28 Days Later, with a storyline about redemption and self-sacrifice that mainstream audiences will find simpatico. Generally well done, the movie owes much of its appeal to star Will Smith. He's adept at choosing timely material. And what's more au courant than crossing a savior narrative with a biological apocalypse of humankind's own making?

All the audience has to do is buy that his character, military virologist Robert Neville, has equal parts brains and brawn. He's Linus Pauling and Mad Max rolled into one. We meet him and his loyal German shepherd, Sam, in a Manhattan eerily deserted after a pandemic has felled ninety-percent of the Earth's inhabitants. The disaster is foreshadowed during a brief prologue in which a guilty-looking scientist (Emma Thompson) announces the cure for cancer on a morning TV show. It is this virus that will mutate, infecting billions and it's Neville who will spearhead the government's scientific response.

In one montage, he's shown, buff and lonely, pumping iron; in the next shot, he's wearing a white lab coat and horn-rimmed glasses while recording data from his experiments to find an antidote. It's risible, although Smith is certainly an actor whom you root for to pull it off. Neville has spent three years staying alive while continuing his efforts to find a cure in the basement laboratory of his Washington Square Park townhouse. He broadcasts a daily SOS asking any survivors to rendezvous with him at the South Street Seaport at midday. When night falls, ravenous, vampire-like zombies emerge -- the people infected with the virus. These standard-issue, computer-generated mutants are familiar from scores of movies released in the last decade. Neville must occasionally trap one in order to monitor the virus and test his antidotes.

Not counting the dog, Manhattan is Smith's real co-star. New Yorkers will relish I Am Legend for the fantasy glimpses of its empty avenues. There's no traffic, no tourists and all the cultural amenities -- like fishing in a pond inside the Metropolitan Museum of Art -- can be enjoyed hassle-free, provided it's daytime and the light-averse mutants won't be a bother. Effectively rendered though not mind-blowing given the ability to embellish via computer, the city is the movie's signature feature and the filmmakers are clearly enamored of it.

Neville's flashbacks to Manhattan as it is about to be quarantined at the beginning of the outbreak are just as impressive. Staging the pandemonium as people storm the bridges to escape must have been a logistical challenge. These exciting segments are admirably succinct and emotionally charged, particularly when Neville rushes to get his wife (Salli Richardson) and daughter off the island before it's sealed.

His failure to ensure their safety earlier, stemming from his dedication to his work, is Neville's primary motivation for becoming a secular savior. Secular, because he expresses doubt in the existence of God. His spiritual guide is Bob Marley, the late Rastafarian musician whom he cites on the power of love. Yet it's no surprise that the story's more traditional religious arc is teased out. Director Francis Lawrence helmed 2005's fire-and-brimstone thriller Constantine, in which Keanu Reeves played a conflicted supernatural hero charged with maintaining equilibrium between God and the Devil. Whereas that flick was a spurious, campy mess, Matheson has provided a solid base for I Am Legend.

Not only does this version feature a non-white hero, toward the end Neville meets a Latina survivor (Alice Braga) who wears a crucifix and has a mute boy (Dash Mihok) in tow. The plight of these trendy stand-ins for the Holy Family comes to a head so rapidly, one suspects a diversionary tactic is being employed so the audience doesn't have time to think. Nevertheless, while it may not be especially deep or original, this iteration of I Am Legend delivers the kind of popular satisfaction that Hollywood fortunes are built on.

(Released by Warner Bros. Pictures and rated "PG-13" for intense sequences of sci-fi action and violence.)