If one were to somehow merge the Scorsese-directed Robert De Niro characters Travis Bickle (of Taxi Driver) and Rupert Pupkin (of The King of Comedy), the result, I imagine, would be someone very much like Lou Bloom, the antiheroic lead played by Jake Gyllenhaal in writer/director Dan Gilroy’s Nightcrawler. From Bickle, he would inherit the nocturnal restlessness and vehicular inclination; from Pupkin, the delusional self-regard and entrepreneurial ambition; and from both, the sense that behind those eyes, some strange, and perhaps dangerous, thoughts are beginning to percolate.

You have to begin with the eyes. They’ve always been Gyllenhaal’s most distinctive feature, but in Nightcrawler they're like parabolic antennae, wide and unblinking, attuned to any signal, however faint. When we first meet Bloom—and indeed, during the bulk of our acquaintance with him—he is prowling the nighttime streets of Los Angeles, eking out his existence as a scavenger. At the outset, he steals: copper wire, manhole covers, anything. When we witness him cutting his way through a chain-link fence, we imagine that he is trying to get to the other side. But no, he’s stealing the fence. When he sells these industrial goods to the owner of a scrap yard, he makes the mistake of asking for a job, prompting the all-too-rational response: “I’m not hiring a fucking thief.”

Later the same night, however, Bloom discovers an alternative form of nocturnal scavengery, when he happens upon a car crash and the freelance cameramen (one played by Bill Paxton) who are filming efforts to pull a victim from the burning wreck. It’s as if Bloom was born for this work, this watching in the darkness—or, more accurately, as if he had evolved for it, his eyes giving him a preternatural advantage, like some deep-sea fish or Gollum from The Hobbit.

Equipping himself with the rudimentary tools of the trade—a camera, a police scanner—Bloom begins his quest for whatever human sufferings he can capture on film and thus commodify: the dying carjack victim, the bicyclist killed by a drunk driver, the murder/suicide. Bloom pokes his camera right into their faces, beyond shame or moral qualm, and then sells the footage to a hard-hearted veteran news exec, Nina (Rene Russo), who is clinging to her job at a bottom-ranked local station. She teaches him what it is she’s looking for: victims (preferably white and well-off) harmed by villains (preferably nonwhite and poor), “proof” to her suburban audience that the inner city is encroaching. And he goes and gets the footage for her.

As Bloom perfects his trade, he acquires a hapless employee (Riz Ahmed), a new fire-red Dodge Challenger, and higher-quality cameras and scanners. He also perfects the art of improvisation, moving from observer to director of his grisly tableaux. Would the shot look better if the accident victim were repositioned more cleanly in the headlights’ glare? If the murderous home invaders are not caught tonight, perhaps they can supply some additional footage tomorrow?

Gyllenhaal is tremendous in the central role of Bloom. Now 33 years old, he is the same age that De Niro was in Taxi Driver and, like him, he is learning to channel an eerie, inner charisma, offering it up in glimpses and glimmers rather than all at once. (In this regard, his performance in last year’s Prisoners offered a worthy warm-up to Nightcrawler’s main event.) Gyllenhaal lost between 20 and 30 pounds for the movie—another echo of young De Niro—in an effort to physically substantiate the animal that he and director Gilroy say inspired Bloom’s character: the coyote, feral native of LA, creeping down from the hills after dark. The effect is most visible in his face, in the sunken pools of his eye sockets and the tight, Joker-rictus of his jaw when he grins. Everything about him says hungry.

Alas, the film overall doesn’t quite live up to its lead performance. This is Gilroy’s rookie outing as a director after working on several screenplays (including that of his brother Tony’s The Bourne Legacy), and his work is smooth and self-assured. Cinematographer Robert Elswit brings his customary flair to the proceedings, shooting with a mixture of film (daytime) and digital (night). And the supporting cast is solid, in particular Russo (who has been married to Gilroy since 1992).

But after a strong setup, the movie descends too frequently into sheer preposterousness. The critique of media voyeurism and its ethos of “if it bleeds, it leads” becomes too broad, and Bloom increasingly gets away with actions that no news station—or, perhaps more to the point, police force—would ever countenance. Is Nightcrawler a sincere commentary on social decay or an over-the-top black satire? Tonally speaking, the movie never quite seems to make up its mind. I’m again reminded of a stitching together of elements from Taxi Driver and The King of Comedy. The result is a very good movie—and a milestone in Gyllenhaal’s career—but one in which the excellent pieces don’t quite fit together.