Jake Gyllenhaal, not a particularly bulky guy to begin with, dropped 20 pounds or so to play a Los Angeles misfit who finds his calling as a freelance crime videographer in Dan Gilroy's nervy thriller Nightcrawler. Even when Robert De Niro does it, weight change isn't acting — it's the antithesis of acting, merely a symbol of an actor's dedication and not the tensile, complicated act of commitment itself, which can unspool only in performance. But you could say that in reshaping his body and face, Gyllenhaal has achieved a kind of art direction of the self. His eyes, almost inhumanly enormous within that now bony face, are as much a part of the look of Nightcrawler as its rapturous nocturnal Los Angeles streetscapes, dotted with palm trees, traffic lights and cheerfully illuminated chain stores. As sociopathic self-starter Louis Bloom, Gyllenhaal has refashioned himself as a version of the Tony Perkins of Psycho, an Adam's apple with a sick, brilliant mind attached.

Gyllenhaal is the polestar of Nightcrawler — just as he's fixated on the grisly crimes and accidents of his city, we can't look away from him. That seems to be part of writer-director Gilroy's design. He's infused Nightcrawler with a number of ideas, free-floating through the movie like fireflies: Gilroy takes on the news media's lust for increasingly prurient stories and graphic news footage, the way crimes against white people take precedence over anything that happens to a person of color, and the downside of citizen journalism in a world where everyone wants to be a star. But on the strength of Gyllenhaal's performance, Nightcrawler works best as a character study. It's chilling but also wickedly funny and strange, like a good, dark Brian De Palma joke — in short, it's everything the stolid and humorless Gone Girl should have been.

Gyllenhaal's Bloom is an eager, intense young man, given to spinning out long, complex sentences in the language of inspirational speakers. That's because everything he's learned, he's learned from the Internet, and scarily, all that knowledge ends up serving him well. As Nightcrawler opens, Louis commits an act of brutality that clearly signals how cracked his conscience is. But he's also weirdly likable, an urban underdog who irons his shirts in front of the TV, chuckling over goofy sight gags from the 1955 Danny Kaye vehicle The Court Jester. Clearly, he's a TCM fan — how can you not want to like him?

By accident — and at the scene of an accident where a woman is just barely pulled from an about-to-explode car — Louis encounters Joe Loder, a freelance journalist, of sorts, played by a half-lumbering, half-swaggering Bill Paxton: Loder chases down potentially gruesome incidents and sells the footage to local TV stations for big bucks. Louis is enthralled, and before long he's bartered a stolen bicycle for a video camera and a police radio from ancient times. (It's emblazoned with the nostalgic brand Realistic.) Rene Russo's flinty-hot Nina Romina, a news director at a flailing TV station, eagerly buys whatever grim footage Louis can come up with, and he's distressingly good at finding it. Pushing his camera into the tightest, bloodiest spaces, he's an heir to Weegee but a dispassionate one.

Louis has no scruples; he's a bundle of raw ambition. He takes on an eager but baffled apprentice, Rick (the quietly magnetic Riz Ahmed), and immediately manipulates him — from there, his misdeeds pile up like a careless driver's tickets. If you're looking for plot realism, go elsewhere: In real life, nobody could obstruct as much justice as Louis does and get away with it. Still, Nightcrawler is unnerving because we never know how far Louis will go. He's sympathetic enough that we wish he wouldn't do these awful things, and malicious enough that we recoil from his apparent naïveté, which is really a kind of shrewdness.

Nightcrawler, shot by the enormously gifted Robert Elswit, is dazzling. The opening-credit sequence is like the movie version of an old-fashioned foldout postcard, a selection of nighttime L.A. delights: Capitol Records, aglow as if it had just touched down from Mars; columns of palm trees whose leaves shimmer in the wind like tinsel; construction sites whose shadowy beams and scaffolding, left by workers for the day, speak of growth and progress, or a new nest of office spaces. Then there are Gyllenhaal's deep, dark eyes, taking it all in. His next big story could come from anywhere: a jackknifed tractor-trailer, a carjacking, a home invasion. He's addicted to looking, and it's our shivery pleasure to watch him do so.

NIGHTCRAWLER | Written and directed by Dan Gilroy | Open Road | Citywide

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