(CNN) -- When Nucky Thompson shot Jimmy Darmody point blank in the head in last season's finale of "Boardwalk Empire," viewers were shocked: How could a father figure kill his surrogate son?
But this is the land of gangsters and bootleggers, and blood isn't the currency here -- it's alcohol. That episode, "To The Lost," nabbed an Emmy nomination for director Tim Van Patten (amongst its many other nods, including best drama and best actor for Steve Buscemi), but it also signified a tonal shift in how the characters on this Prohibition-era drama would operate in the next season, which kicks off Sunday, September 16 on HBO: no more Mr. Nice Guy.
As the show jumps ahead to New Year's Eve in 1922, "the stakes are higher," said showrunner Terence Winter.
"The '20s had really started to roar, so it's when radio was everywhere, music made the charts, and the flapper as we know her started to come out," Winter said. "The economy had started to boom, which lead to young people buying cars and traveling more from home. And while a lot of people had stockpiled alcohol, by 1923, they were running out, so there was a lot more competition (in bootlegging) and it became a lot more violent. It's the era of the Tommy-gun."
So while Nucky survived an attempted coup on his market share last season, in order to stay on top, he has to try new strategies, which includes streamlining -- instead of selling to multiple buyers, he wants to sell to only one -- and those cut out of the supply line are none too pleased, including a hot-tempered new antagonist named Gyp Rosetti, played by Bobby Cannavale. "A guy like that, he's got such a hair trigger, you could end up dead over something you said that you didn't even know was taken as an insult," Winter said.
"There's an upcoming line where Nucky says, 'Gyp Rosetti can find an insult in a bouquet of roses.' "
The audience's introduction to Rosetti comes when he has car trouble, and he requires assistance to fix his tire from a helpful stranger who is out walking his dog to fix his tire. The pooch plays a role in what follows and it's the type of touch that may give audiences some pretty good insight into Rosetti's character.
"It's a very funny idea," Cannavale said. "You get to see guys like Nucky who are more professional in the way they go about their work, and this guy, it seems like he might be in the wrong profession, you know? He's got a lot of zingers, which is good, because that's how I'm like in real life. My favorite line is when I call Steve (Buscemi) 'a breadstick with a bow tie.' "
Nucky takes that one in stride, for now -- but he's not too keen on taking any guff from his wife Margaret anymore, as he's not about to forgive her actions last season, when she signed over a tract of land he bought between Atlantic City and Philadelphia to the Catholic Church shortly after their wedding ceremony. Their union is now a shaky one, and Margaret finds herself in a tricky position.
"I'm just delighted that she's not passive anymore," said Kelly Macdonald, who plays Margaret. "She knows how to look after herself, and she's becoming stronger. She's very complex. You never quite know where she's going to go next."
Married or not, Nucky shares his bed with new flapper/showgirl Billy Kent, played by Meg Steele.
"She's a fun girl," Steele said of her character. "The flappers weren't feminists, but they were enjoying the new-found feminism. So she's living life to the fullest, and she has her own apartment, her own life. She's not as needy as (Nucky's former mistress) Lucy was."
Speaking of Lucy, Winter said it's "a long shot" that we'll see her again, even if her child is now being raised by Michael Shannon's character. The disgraced Prohibition agent Nelson Van Alden is now living under an assumed name as a door-to-door salesman in Cicero, Illinois, which puts him in proximity with Al Capone's power base.
"I don't have a gun, and I don't make whiskey in my bathtub, so I don't identify with these people much!" Shannon laughed. "But Van Alden is still in hiding."
"He's constantly dealing with the fact that he could be caught, arrested, and sent to jail for the rest of his life," the actor added. "He's got a family to take care of. And he lost a pretty good job, so now he's faced with a pretty harsh economic reality, because it's a hard time to make a living and support yourself. I don't think he can really see himself as a lawman anymore."
Like Cannavale's character, Van Alden is now in a position that's ripe for both tragedy and comedy, particularly when he accidentally walks into a turf war between Capone and Dean O'Banion, a real-life adversary of Capone's who also worked as a florist.
"Even if the storyline is dark or something bad happens, it doesn't mean it's not fun to do it," Shannon said. "But Van Alden is never going to have an easy time on this show. That's not why he's on the show. He's a tragic character, and the tragedy is going to unfold."
Still reeling from their own personal tragedy, in the aftermath of the deaths of both Jimmy and Angela Darmody, Gillian Darmody and Richard Harrow are raising Tommy Darmody together. This is not without some tension, since Gillian wants to be considered Tommy's mother, not his grandmother, while Richard tries to help the boy remember Angela.
"I've become the surrogate au pair, for a lot of it," said Jack Huston, who plays Harrow. "I would think Angela would want Tommy to be very far away from Gillian and the kind of opportunities of what that show is about," laughed Aleksa Palladino, who played Angela. "Richard is the better parent for Tommy."
But Gillian being Gillian, has always got a scheme up her sleeve. "For her, it's about power," said Gretchen Moll. "It's really fun, because that's not where I love. I'm not really an angry person. But she's trying to figure out her next move. It comes out as the season unfolds."
Could that mean a revenge plot against Nucky for killing Jimmy and leaving his son an orphan? An alliance between Van Alden and Al Capone? Who will be in power and who will die? The cast won't reveal trade secrets, but they all hint the new season will be more explosive than the last.
"It's an amazing time for TV drama," showrunner Winter said. "It's daunting to even think we're competing against "Breaking Bad," "Homeland," "Downton Abbey," "Game of Thrones," and "Mad Men" in any category, let alone best drama. It's thrilling, and I don't even mean to sound humble."
"Was I disappointed about Michael? Winter said, referring to Michael Pitt, who didn't get nominated for his portrayal of Jimmy Darmody. Yes, because he was terrific, but who knows how this works? And we have an amazing supportive cast -- Michael K. Williams, Michael Shannon, Michael Stuhlbarg, any other Michael on the show. And you don't have to be named Michael to be on the show anymore. You can be named Bobby."