Unfailingly polite, easygoing and humble — unlike the hard-driven, obsessive producers at the helm of many quality dramas — Gilligan was uncertain whether there was an audience prepared for the darkness of his sinister brainchild. There was initial resistance: FX, which has a reputation for producing edgy material, was among the networks that passed on his pilot script.

Even after AMC picked up the series, he never envisioned "Breaking Bad" lasting six years: "Not even close. I thought we were lucky to make the pilot in the first place. Once we were up and running, I would have said we would last two seasons, maybe at the outside four seasons."

VIDEO: Anna Gunn on 'Breaking Bad'

Said Jamie Erlicht, president, programming for Sony Pictures Television, which produces the show: "We knew a series like this wouldn't be easy. Most networks eliminated the concept right off the bat. But we knew it was an idea that would pay dividends."

"Breaking Bad" received immediate critical acclaim during the first season, which only grew (said Variety's Brian Lowry, "For a show about meth cookers, 'Breaking Bad' is simply one of TV's great addictions."). Cranston's three consecutive Emmy victories for lead actor in a drama series boosted interest, and viewership increased.

The innocuous story line of the pilot that had echoes of "Les Misérables" — a mild-mannered man who turns to crime temporarily to provide for his family — evolved into a universe clouded by blurred morality, brutality and over-the-top characters: Walt indirectly caused a plane collision that killed hundreds; a fast-food chicken chain was the front for an elaborate meth-selling operation. Ruthless drug kingpin Gus Fring (Giancarlo Esposito) slashed the throat of an accomplice with a box cutter and threatened Walter's family. Walt then planned an elaborate revenge scheme that ended with Fring's face being blown off in an explosion at a nursing home.

The raves were universal. Though he admired it, The Times' Robert Lloyd felt in the show's later years that White's story arc was wearying: "Walt has long since crossed the line in which it is possible for me to feel for him."

"Breaking Bad" opened its fifth season last July to its largest audience, some 2.9 million viewers. Along with "Mad Men," "The Walking Dead" and "The Killing," the series was also pivotal in establishing AMC's elite status in the cable universe.

PHOTOS: Behind the scenes of 'Breaking Bad'

It also caught the first wave of a new phenomenon that was unheard of when it premiered — binge viewing. As buzz over the show grew, the curious began checking out the earlier seasons on DVDs and streaming services.

"It was pure dumb luck," Gilligan said, typically low-key. "We timed it perfectly. I know we were on the bubble at the beginning, but binge watching saved our bacon."

Thrilling endgame

In an interview last year before the final half of the season was written, Gilligan suggested that White should go straight to hell, that extremely evil people need to be punished for their misdeeds.

Whether that philosophy is carried out is being guarded with National Security Agency-level stealth. But for Gilligan, the cast and producers at Sony, the end of the journey has been simultaneously exhilarating and wrenching.

Cranston, who just scored another lead actor Emmy nomination, said the countdown to the final installments has been "a mixture of dread, anxiety, excitement and thrills. There's been a lot of tears, rejoicing and lamenting. The full spectrum. The whole thing ends in a very 'Breaking Bad' way. I think fans will embrace it."

Anna Gunn, who plays White's embittered wife, Skylar, and was also nominated this year for an Emmy, said there were scenes that "were difficult and emotional."

Emmys 2013: Top nominees | Complete list

Sitting in a darkened room of the studio during a break, Paul, who was again nominated for his role as Pinkman, seemed the most upset about the approaching end. "My heart starts to race a little when I think about it," he said. He decided to relive his "Breaking Bad" experience by watching all the episodes from the pilot. "It's very hard to let go," he said.

Gilligan appears to be a bit more at peace. Just a few weeks before the farewell hoopla began ramping up, he sat among several boxes in his Burbank office containing props, mementos and story notes.

The toys, puzzles and Play-Doh that Gilligan and his writing staff had fidgeted with during brainstorming sessions had been packed away. Still unboxed and on a shelf by itself was a clay figurine of a severed head on top of a tortoise, one of "Breaking Bad's'' more gruesome — and darkly humorous — images.

"I'm really happy to say, as sad as I am to be sitting in this office, with these boxes all around me, the one thing I haven't lost any sleep over, the one thing I'm not sad about, is that we're ending it now," he said. "I don't think we overstayed our welcome, not for a minute. That was a big concern for me."

Now that the series is edited, some members of the troupe have moved on. Cranston is preparing to play President Lyndon B. Johnson in the American Repertory Theater premiere production of Robert Schenkkan's "All The Way" in Cambridge, Mass., in September. Gilligan is excited about developing a possible "Breaking Bad" spinoff that would feature Saul Goodman, the shady lawyer played by Bob Odenkirk that was one of the show's more humorous characters.

Gilligan is making one promise to "Breaking Bad" fans about the finale: "To quote a famous movie, there will be blood," he vowed with a wicked chuckle.