Jake Gyllenhaal in “Nightcrawler.” (Open Road Films)

If Dan Gilroy’s Nightcrawler (rated R) is a love letter to Los Angeles and television news, that letter is written with letters cut out from newspapers and magazines – like a ransom note from an unhinged stalker. There’s a jittery mania to the proceedings, an edge of barely controlled overenthusiasm, that suggests too many nights with too little sleep and too much caffeine. Like its lead character, the film is streamlined, determined and unforgettable – but you’ll still want to shower after you meet it.

Much of the film’s success is borne on the bony shoulders of Lou Bloom, a misfit creation from the mind and emaciated body of Jake Gyllenhaal. Lou is a sociopath, and Gilroy’s film (he also wrote the screenplay) makes a strong, dispassionate argument for that mental state being sadly effective in getting ahead in one’s chosen career. We first meet Lou in the act of stealing scrap metal at night, and dispatching a security guard who tries to stop him; Lou notices the guard’s fancy wristwatch before he assaults the watchman, and the film periodically checks in on Lou’s wrist, where the ill-fitting watch dangles like a gaudy trophy of an early kill.

But Nightcrawler isn’t a thriller in that sense. Almost immediately Lou finds the work he was born to do, when he stumbles upon a car crash and is transfixed by the adrenalized professionalism he sees in the freelance camera crews that descend upon the human carnage to scoop up images to be sold to the evening news. You can see Lou thinking, I can do this; and before long he’s surfing the channels of a cheap police scanner and racing around town with the best – or the worst – of them.

Gilroy, a journeyman screenwriter (Two For the Money, The Bourne Legacy) making his directorial debut, has nothing new to say about the deplorable “If it bleeds, it leads” mantra of our electronic news age. What’s different is how he says it – with lenswork that depicts nighttime Los Angeles with the same glittering feverishness found in Michael Mann’s best films – and in his onscreen mouthpiece for that borrowed philosophy of media misanthropy. As Lou, Gyllenhaal is an alien creature poured awkwardly into human skin: Armed with zero social skills save for those he’s absorbed from self-help websites, he skitters into the frame and disarms everyone he meets with a transparent agenda and an unblinking gaze. Lou sees everything, making him an eager student of whatever he chooses to study and the ultimate spectator at the scene of a violent crime. He’s definitively creepy – the kind of creepy that gets noticed at Oscar time.

The peril of having such a dynamic central character, of course, is that everyone else around him will seem flat. In that, Rene Russo saves the day as an overnight news producer for the number-three L.A. station who doesn’t have time to be repulsed by Lou or his antics; in fact, she tutors him – until the pupil quickly turns the tables on the mentor, and dangles increasingly lurid footage in front of her face until she gives him what he wants. Like too many women of a certain age, Russo has had a tough time in Hollywood in recent years, but she contributes the strongest work of her career as a career woman who’s been so ground down by fear and eroding professional ethics that she can’t tell what a toxic partnership looks like until it’s too late. Nightcrawler is far from perfect, but with these two performances against a captivating perspective of the tainted City of Angels, it’s hard not to describe it as a must-see.