One chief delight, for me anyway, of the high-end cable drama is the opportunity to become enveloped in a lushly conjured world with its own history, geography, and social codes—a world which, over years of watching, can begin to seem not just plausible, but real. Mark Bowden once remarked that when he walks around his native city of Baltimore, he half expects to run into characters from “The Wire.”

But how realistic these worlds seem may depend, in part, on where you sit. Many journalists were evangelical fans of “The Wire” during its first four seasons, praising the exquisitely accurate depiction of hustlers and junkies on the streets of Baltimore. But in Season 5, when David Simon turned his clinical eye on a milieu the journalists actually knew something about—a contemporary newsroom—they reviled the show as unrealistic.

“Breaking Bad,” which returns for its fifth and final season this Sunday, premièred in the same year as the last season of “The Wire,” and also concerns itself with the drug trade. But the two shows couldn’t be more different: whereas Simon favored an almost vérité austerity in his filmmaking, Vince Gilligan opts for Technicolor landscapes, hallucinogenic visuals, and a whole bag of narrative tricks (flashbacks, flash-forwards, montages, music videos, etc.) that Simon almost entirely disdained. Whereas “The Wire” had a sprawling cast of dozens of major characters, “Breaking Bad” is a chamber piece, relying on the shifting alliances and betrayals of the same handful of players. The show presents a challenge, for Gilligan and his writers, to configure and reconfigure, like playing an endless game of Scrabble using only the same eight letters.

So it’s somewhat surprising that in depicting the mechanics of the meth business, “Breaking Bad” is so notably realistic. I spent the past six months interviewing drug traffickers and D.E.A. agents for an article about the business side of a Mexican drug cartel, and, having been an ardent fan of “Breaking Bad,” I was startled by how much the show gets right. On one level, the show is a parable about the impossibility of running a mom-and-pop business in a world of rapacious multinational conglomerates. In this sense, it shares a basic template with Oliver Stone’s lurid “Savages”—or, for that matter, with “You’ve Got Mail.” The difference in the case of Walter White, the show’s protagonist, is that Pop ends up waging bloody war on the conglomerate. And winning.

“You know the business and I know the chemistry,” Walt tells Jesse Pinkman, the inept but soulful hoodrat who is his principal accomplice. Walt creates a premium product: pure, wildly addictive blue meth. But in a clandestine industry, having a quality product isn’t enough. You need distribution. Selling drugs on the street is a risky job, and generally falls to the most dispensable folks, in this case Pinkman’s knucklehead associates Badger, Skinny P, and the portly, mohawked Combo (R.I.P.). Consider this impeccable, hilarious scene (with a priceless cameo from D. J. Qualls), shot almost entirely in a long take, as a one-act object lesson in the hazards of street distribution.

As Walter’s business grows, his needs outstrip the limited abilities of his sales force. This is a constant problem for drug runners. I spoke with one longtime trafficker who told me that a recurring liability in any scheme is the inclusion of some friend or cousin who invariably turns out to be a drunk or a junkie. When Pinkman has the wickedly ingenious idea of sending Skinny P and Badger to join a twelve-step program in order to sling their product to fellow addicts, they end up selling their meth to one another instead. As if that’s not bad enough, they then proceed to fall into the program themselves. (“Homey, I’m on step five,” Skinny P tells a furious Pinkman, with endearing pride.)

“We need a proper infrastructure,” Walter eventually concludes—a buffer that will insulate them from the dangers of the street. (“Layered,” is how Pinkman characterizes this arrangement. “Like nachos.”) For help in this regard, they turn to Saul Goodman (J.D., University of American Samoa), no mere criminal lawyer, Pinkman points out, but a criminal lawyer.

With his questionable legal advice (“If a prison shanking is completely off the table…”) and incriminating maxims (“I don’t take bribes from strangers”), Saul might seem the most caricature-like creation of the show. But believe me when I tell you that I have met lawyers like this. It takes a special brew of amorality and pluck to represent a drug lord, and Saul is an only slightly exaggerated version of some very real attorneys who ply our Southwest border.

By Season 4, Walter is earning seven million dollars a year, and how to launder large amounts of money is a perennial challenge for narcotics professionals. Saul, as the sort of quasi-legitimate “facilitator” who serves as a hinge between the licit and illicit worlds, is typical of a breed of lawyers, money managers, accountants, and bankers who earn a parasitic living off the fortunes of the drug trade. Actual cartels prefer businesses like soccer stadiums or used-car lots to launder their money, because the books can be easily cooked. So when Walter’s wife Skyler suggests buying the car wash where he used to work, she definitely has the right idea. (Though in a pinch, Saul’s suggestion—“Laser tag!”—might have sufficed.)

Saul also introduces Walter to Gus Fring, the brilliantly realized and also surprisingly realistic meth-king proprietor of the Los Pollos Hermanos chicken chain. Flashy drug dealers in the Scarface mode make for enjoyable movie villains, but in real life they don’t tend to last long in the business. Quiet businessmen like Gus, on the other hand, often thrive. In his lack of ostentation and attention to detail, Gus is typical of a certain kind of successful drug professional. Risk averse by temperament, he doesn’t drive a Ferrari, but a Volvo station wagon.

The one feature in the show that is most glaringly off is the gleaming subterranean mega-lab that Gus constructs for Walter. To be sure, labs like these exist—just not in the United States. One major challenge for any meth producer, which gets scant attention on the show, is how to source adequate precursor chemicals, which are heavily regulated in the States. In real life, it would be impractical to undertake the sort of industrial-scale production that Walter does (two hundred pounds a week) inside this country, because of the difficulty of acquiring the necessary chemicals. It is much easier to shift production to Mexico or Guatemala, as the major drug cartels have done, where mega-labs (that dwarf Walter’s) churn out meth for export to the U.S. Meth is still cooked in this country, but generally in smaller “shake and bake” batches more typical of what you see in “Winter’s Bone.”

Otherwise, the show’s portrayal of Mexican cartels is devastatingly accurate. It has been suggested that Vince Gilligan has a sick mind, but nothing he could dream up, even the unfortunate fate of Tortuga, can rival the creative barbarism of the cartels. Many viewers were repulsed when Walt and Pinkman used acid to melt a body in an early episode, but this is such a common disposal technique in Mexico today that it has acquired a nickname—the guiso, or “stew.” One plot device that drives much of the third and fourth seasons is the notion that Walt is irreplaceable (and therefore, likely to survive) only until someone else, whether his lab assistant Gale, or Jesse Pinkman, can learn to reproduce his recipe. A federal prosecutor in California told me recently about a case in which a group of American ecstasy producers entered negotiations with a Mexican cartel to manufacture large volumes of the drug, but ended up abandoning the deal when they realized that the cartel intended to keep them around just long enough to learn their recipe, then kill them.

This may be the scariest aspect of “Breaking Bad,” and of the drug trade itself: the more ghoulish and extreme the show becomes, the more it seems to traffic not in realism but in horror, and the more accurately it captures the reality of the cartels and their business.

Photograph: AMC.