I Am Legend, the third film based on Richard Matheson’s 1954 science fiction novel, moves as speedily as the infected freaks who terrorize the story’s apparent last man standing; the hero’s fate is sealed and the credits are rolling barely after you’ve managed to tune out the blabbermouth behind you. But a thriller that feels shorter than an episode of Lost won’t elicit nightmares as much as a big so-what—after all, if a horror movie is of true holy-bejesus caliber, you should be exhaling with relief at the end instead of thinking, “Gee, that went fast!” Will Smith stars as Robert, a military scientist who decides to stay in Manhattan when his family and the rest of the island are evacuated during an epidemic. He’s sure he can find an antidote to a virus that itself was touted as a cure for cancer, but a few years after the quarantine, New York’s streets are overgrown with weeds, and Robert is alone with his German shepherd, Sam. He and Sam venture out by day, speeding through the city in a Mustang (which is exhilarating to watch, though you wonder what the hurry is) to look for food, visit the video store, and retain some sense of routine/sanity. Then they lock themselves down at night, hiding from the hairless, angry hordes of a vampire-zombie mix called “dark seekers.” An empty city, a sole survivor, a “virus” that can rightly be modified with “rage”—yes, it’s all very 28 Days Later, except, well, it’s not as good. Director Francis Lawrence lowers his game by resorting to cheap scares, the absence of which is pretty much all that saved his only other feature, 2005’s Constantine, from being completely laughable. There are a few deftly tense sequences here—one in which Robert chases Sam into a dark alley is a highlight—and Smith is a worthy enough lead, tamping down his quippage and expressing anger without a single “Aww, haaalll no!” Horror fans looking for more substantive entertainment, however, might find that phrase useful.