ALBUQUERQUE

WALTER WHITE was a sympathetic innocent when AMC’s descent-into-darkness television series, “Breaking Bad,” began in 2008, a cancer-stricken chemistry teacher who — ostensibly to support his family — began to manufacture crystal meth. But he didn’t stay innocent for long. He has become a murderer, a liar, the kind of man who lets a girl overdose as he watches, because she’s gotten in his way.

The premise of the series, which returns on Sunday, following Walter White’s transformation from a decent man in desperate circumstances into a ruthless drug lord, always seemed made for a short run. How could Vince Gilligan, the soft-spoken Virginian who created “Breaking Bad,” possibly sustain the dark tone and high stakes for another season?

Actually, what Mr. Gilligan wants before the series ends, is even more bleak: to remove all vestiges of likability from Walter White, to complete a transformation unlike anything a television series has ever tried.

“There will be a point for everyone when they finally stop sympathizing with Walter White,” Mr. Gilligan said. “It’ll occur at different times for different people. In the early going it was quite easy to see him as a good man who was trying hard to do the right thing.