Aaron Paul and Bryan Cranston

In the fifth season of Breaking Bad, Walter White truly is The One Who Knocks.

The AMC drama's Season 4 finale saw Walt (Bryan Cranston) — the one-time cancer-stricken high school chemistry teacher who began cooking meth to provide for his family after his death — pull out all the stops to protect his loved ones and his partner Jesse (Aaron Paul) from the terrifying drug kingpin Gus Fring (Giancarlo Esposito). After blowing up Gus in gruesomely memorable fashion, creator Vince Gilligan says he feared he'd never be able to fill the void.

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"In the early going of figuring out Season 5, we said to ourselves, 'Wow, who's next? Who's badder than Gus Fring?'" Gilligan tells TVGuide.com. "Then we thought to ourselves, 'We've got a guy who's badder than Gus Fring. He's the guy who killed him for goodness sake!' Walter White really is the guy. He's the new king. He did win, and to the victor go the spoils. And in Season 5, Walt, having ascended to the throne, will now be faced with what it means to be king. How will he fare at being in charge? Will it be all that he wanted it to be and more, or will it somehow be less?"

But now that he's safe, why would Walt keep cooking at all? Although Walt argues this season that there is "gold in the streets" waiting to be scooped up, Gilligan warns viewers to be wary of Walt's rationale. "Meth is a hugely addictive drug, but it seems to me the process of making meth and the process of deriving money and power from it is itself addictive for Walt," Gilligan says. "The money is always an excellent excuse for Walt, but it's not really what drives him. Walt is a self-rationalizing character who just lies to himself over and over again about the reasons he does the things he does."

Walt's true motivation is his ego, Cranston says. "One would think that you go, 'Oh, thank God that's over. Let's get the hell out of Dodge,'" he says. "But Walt does the opposite. He says, 'Look what I did. Look at me. You want to know who's running things? Look at that!' So he has adrenaline, which is a drug that he's never tasted before that he really loves. That's pumping through his veins and he's feeding off it like a wild animal."

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This vicious new side to Walt will be clear to everyone in his orbit. His wife Skyler (Anna Gunn) is visibly frightened to be in the same room with Walt and Walt's attorney Saul (Bob Odenkirk) cowers in his presence during a meeting. Ditto Jesse. "He slowly starts to become pretty scared of Walt, but I think everyone does," Paul says. "That's the theme of this entire season. This year it's just more eerie. You want to take a shower after you read these scripts. You just feel dirty. It's so unbelievably creepy and dark and flat-out scary."

Jesse is perhaps the one with the most to fear. The Season 4 finale's most chilling reveal was that Walt, not Gus, had in fact poisoned Jesse's girlfriend's son. The move brought Jesse back under Walt's wing and was perhaps the final step in Walt's transformation from his former self into his evil drug lord alter ego Heisenberg.

"When you're talking about this kind of life, a lot of being equipped to operate in this [world] comes down to the very base question: Are you capable of killing another human being and moving on? And he now is," Cranston says. "In any kind of confrontation or sporting event, the team that's victorious is the one that's willing to go all the way and put every single bit of effort out on the field. Walter White is clearly indicating that he is willing to do whatever it takes."

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Gilligan, who initially pitched the series as an exercise in turning Mr. Chips into Scarface, says that Walt's manipulation of Jesse is perhaps his greatest evil. "Walt is darker at the beginning of Season 5 than I ever thought he would become," Gilligan says. "[The Scarface analogy] seems to be wearing more and more thin as the show progresses because Walt is much more Machiavellian these days. He is a master manipulator. The way he manipulates Jesse is monstrous. We saw the height of it at the end of Season 4, and, fortunately or unfortunately, we have more examples of it to come."

Adds Cranston: "You think you've seen the depth of where Walt can go, but you'll realize, 'Oh, I guess I haven't. He's going darker and deeper.' Anybody who needs to root for the lead character and be in league with them at all times has long since turned this show off. This is a train straight to hell, and for some reason, people want to be on the ride."

However, Gilligan argues that Walt cares deeply for Jesse. "Walt needs Jesse on a certain level," Gilligan says. "He needs a loyal partner; he needs the backup. But beyond that, some days it seems like he needs more still. Jesse being in his life seems to be of utmost importance to him, and it's clear he will do anything to keep Jesse's respect and keep Jesse's obedience."

Of course, Walt and Jesse aren't truly out of the woods yet. In the premiere (Sunday at 10/9c, AMC), they will have to contend with a very angry Mike (Jonathan Banks), Gus' former right hand. Fortunately for Walt and Jesse, Mike can't just kill them; he must help tie up a few dangerous loose ends first. In doing so, viewers will meet some of the power players above Gus, who also end up on the radar of Hank (Dean Norris), Walt's DEA agent brother-in-law who, after Gus' death, is reinvigorated in his hunt for Hesienberg.

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Although Walt is more confident in his skills than ever, Gilligan warns that Walt certainly shouldn't be too proud to underestimate these new threats. In other words, Walt may not be the king for long.

"Walt has shown thus far that he's capable of taking on all comers and there's no reason to think that won't continue," Gilligan says. "On the other hand, there's no reason to think that there's going to be a happy ending to this show. Indeed, pride does goeth before a fall. Walt is higher up the totem pole than he's ever been and therefore has more to lose and a greater distance to fall. Whether or not he will cling by his finger tips to the top of the heap remains to be seen, but one can intuit from how hard it's been for Walt to get here that it's not going to be all peaches and cream from here on out."

Breaking Bad airs Sundays at 10/9c on AMC.