In an episode midway through the second season of “Breaking Bad,” Walter White was honored with his very own narco-corrido, a song (performed in a precredit sequence by the group Los Cuates de Sinaloa) that spread the legend of “Heisenberg” across the border from New to Old Mexico and foreshadowed his clashes with the cartel competition. “This homie is already dead; he just doesn’t know it yet,” the lyrics warned, and of course the joke was that, at the time, Walter’s unlikely career as a drug kingpin was made possible by exactly such knowledge. As far as he or anyone else could tell — apart, perhaps, from Vince Gilligan, the creator of the series and the ultimate master of Walter’s fate — cancer would finish Heisenberg long before any cartel hit man got to him.

Now, five years in, the cable-watching public is awaiting the final stanzas next month in the Ballad of Walter White, who has evolved into a complicated and very contemporary folk hero. His Heisenberg pseudonym was borrowed from the physicist whose uncertainty principle is popularly understood to express the idea that the presence of an observer changes the nature of what is observed. And Walter, a sad-sack high school chemistry teacher who found a vocation cooking the finest methamphetamine money could buy, was always adept at shifting his appearance depending on who was watching.

In truth, though, his development over five seasons has been less a shocking transformation than a series of confirmations. Mr. Gilligan’s busy and inventive narrative machinery has provided plenty of cleverly executed surprises, but these have all served to reveal the Walter White who was there all along. The sides of his personality — sociopath and family man, scientist and killer, rational being and creature of impulse, entrepreneur and loser — are not necessarily as contradictory as we might have supposed.