Based on Richard Matheson's novel (previously filmed as "The Last Man on Earth" and "The Omega Man"), the movie is set in 2012, when a virus has killed the vast majority of the world's population. Of the few million people left alive, most have turned into cannibalistic zombie vampire-y things, preying on whatever animals or people they can find.
Then there's Dr. Robert Neville (Will Smith), a military scientist. He and a tiny percentage of other people were strangely immune to the virus. He was tasked with helping prevent the outbreak; that having failed, he now works feverishly to devise a vaccine. The cannibal zombie vampires are still human beings and can theoretically be made well again.
Accompanied by his trusty German shepherd Sam, Robert hunts the deer that now live in Manhattan (but look out for lions!) and makes daily trips to the video store. He has gasoline and water and electricity at his heavily barricaded home/laboratory. He always makes sure to be home well before dark, to prevent any of the infected from following him and discovering where he lives.
Will Smith has the same kind of everyman likability that has made Tom Hanks the world's biggest movie star, and he has the same obligation here that Hanks had in "Cast Away": to keep the audience's interest despite being alone on the screen. Smith manages that exceedingly well, with one particular sequence of events reinforcing his loneliness and grief so vividly that it actually brought tears to my eyes. He is a fine actor, let us not forget, in addition to being a butt-kicking action hero.
He gets to flex both sets of muscles in "I Am Legend," as Robert inevitably encounters nests of infected folks and must kill, evade, or capture them. Lawrence creates spooky tension with all that silence, piling on more creepiness as we realize the zombies are starting to get smarter.
That brings me to one of the problems I have with the screenplay, which was adapted (not very faithfully) by Mark Protosevich ("Poseidon") and Akiva Goldsman ("Batman & Robin," "Practical Magic," "I, Robot," several other bad movies) from Matheson's novel. Robert is obsessed with curing the monsters, suggesting he realizes they are not beyond hope. Yet he also insists they have no shred of humanity left, despite several very obvious signs that they do. If he's so pessimistic about them that he's willfully ignoring evidence of their humanity, then why is he also determined to cure them? Those two mindsets are at odds with each other.
Robert is a tragic, bleak figure. You might wonder why a movie like this is coming out in December instead of during the summer blockbuster season; you won't wonder after you see it. In flashbacks, we see him hustling his wife (Salli Richardson) and daughter (Willow Smith) out of New York just before a quarantine is imposed. "I can still fix this," he says, even though things are already bad enough that such a declaration is ludicrous. He says it again later in the film. By that time, it's downright pathetic. You feel for the guy.
The decision to create the zombies with computers instead of good old-fashioned actors in makeup does not pay off; they never look any better than video game characters. That and some sogginess in the film's last act (when he plays the Bob Marley CD for someone -- oy vey) prevent me from loving it. Nonetheless, the silence, the suspense, and Smith's accessible performance draw you in for some post-apocalyptic fun. The end of the world is almost always a hoot.