The 12-episode first season (a second has already been shown in Europe) centers on two members of a drug gang in the Naples suburbs who are like a foster-family version of Sonny and Michael Corleone. Gennaro (Salvatore Esposito) is a Sonny-like hothead, unfit to be in charge but eventually thrust into the role because he’s the only son of the boss. Ciro (Marco D’Amore, whose quiet charisma holds your attention) is a coldly efficient killer and canny strategist — he’s the Michael, but because he’s not in the family, he has to work with Gennaro, or appear to.

The relationship of these two up-and-comers, playing out amid a large cast of other familiar Mafia-drama types (the ruthless but declining boss, the calculating mother, the good soldier, the aggrieved wife), proceeds through an arc of increasingly operatic violence, as rival clans fight for turf and one massacre begets another. The story line is dark, and so is the screen. Under the guidance of the showrunner, Stefano Sollima, the show makes a fetish of low light and shadow. Its most characteristic scenes are not chases and shootouts but small groups of nervous or celebratory men meeting in the dark. They gather on street corners, in crowded discos and in abandoned buildings that serve as drug markets, their faces obscured or invisible. Even during the day, they’re in curtained rooms or prison cells.

The cinematography and lighting fit with the show’s overall sense of desolation, a depiction of the Neapolitan environment as rubble-filled, overgrown and derelict. (Scenes set in Milan offer a pointed comparison to the less prosperous south.) Much of the action is set in faceless, towering apartment blocks that recall the settings of Italian neorealist films, though touches of lyricism creep in, like a beach scene in which a pair of horse carts passing in the background feel like early Fellini.

Mr. Sollima and his colleagues are certainly aware of the many influences to be sorted through in making a modern gangster tale. At one point a young hood, describing the botched job that got him imprisoned, says that cops and helicopters arrived “just like an American movie.” In “Gomorrah,” they’ve achieved a satisfying international blend.