"It's almost playing a different character, but within the same person," Paul tells TVGuide.com. "This show is about change, and all the characters are kind of morphing into different parts of themselves. And this season it's just so much — they're so in over their heads and it's so much darker."
Jesse certainly has plenty to fear. Despite being in rehab, he's decided to continue cooking meth the way Walt (Bryan Cranston) taught him. In last week's episode, that decision led Walt's DEA Agent brother-in-law, Hank (Dean Norris), right to the door of Walt and Jesse's meth-lab RV. Though Walt's quick-thinking got the duo out of the jam, Jesse still has a price to pay in Sunday's episode (10/9c on AMC).
"Some things go down that put Jesse in a very dark place, a place we've really never truly seen Jesse go before," Paul says. "He's just over it. It was his boiling point. He has lost everything, and there's no really point to any of this anymore."
Walt is the target of Jesse's boiled-over rage, and the end result is a powerful scene that will surely make Paul's Emmy tape and could even earn him a second-straight nomination.
"Everything starts to simmer inside of Jesse," Paul says. "Since Day 1, Walt has turned Jesse's life upside down. Jesse was very happy living his mediocre life. He was comfortable dime-bagging it. ... So, he's like, 'I don't need you; I'm doing this on my own — just go f--k yourself.'"
Paul says viewers are right to be worried about Jesse continuing to dabble in the meth business, given his history as an addict. "It's definitely skating on thin ice," Paul says. "The temptation's always there, but Jesse's very adamant about staying clean, particularly because he's feeling so unbelievably guilty. It's a gamble but we'll see."
The guilt stems from the death of Jesse's girlfriend Jane (Krysten Ritter), who he pulled off the wagon in Season 2. But since Jesse doesn't know that Walt watched Jane die without intervening, the Walt-Jesse relationship stands to get even more strained if the truth comes out. Paul promises that issue will be addressed, and that the season's last two episodes will be especially "mind-blowing."
"Questions will be answered by the end of the season," he says. "But what's so great about this show is you never truly see what's coming next. If you think you know what's going to happen, something quite the opposite will happen."