"I'm a philanthropist now," Nucky Thompson insists in the third season premiere of HBO's "Boardwalk Empire." (It returns Sunday night at 9.)
 
"You're a gangster, plain and simple," he's told.
 
This should be welcome news for fans of the period drama. In the series' very first episode, Nucky's protégé Jimmy Darmody warned him that, with Prohibition's arrival, "You can't be half a gangster, Nucky. Not anymore." The first two seasons chronicled that slow and steady path for Nucky, from corrupt but largely non-violent politician, to a man who would order attacks on his enemies, to the man who in last season's finale held the gun himself when it was time to execute Jimmy for going to war against Nucky and losing.
 
Because Nucky was such an ambivalent wiseguy, and because Steve Buscemi's performance in the role is often deliberately opaque (Nucky will reveal himself, but rarely when and with whom you might expect), much of the juice of those first two seasons came from Michael Pitt's performance as Jimmy. But the Jimmy/Nucky war meant that one of those characters would have to kill the other — unless "Boardwalk" creator Terence Winter just wanted to avoid the dramatic implications of his own story — and it wasn't going to be the guy who's the only character to appear in the show's opening credits sequence.
 
In that sequence, of course, Nucky stands on the beach at Atlantic City, letting the surf wash over his shoes, lost in thought and not entirely pleased as one bottle after another of illegal booze winds up on the sand. The waves recede, and Nucky quietly walks back towards the boardwalk. It's a pretty string of images, but one that depicts the show's main character as passive and cerebral, letting action happen around him but doing nothing about it. That's not exactly who he's been on the show itself, but it's close enough that I had great hope that Jimmy's murder would transform Nucky into a more active, dynamic character to help fill the void left by Pitt's exit.
 
And that happens a good deal of the time in the third season. Nucky's first scene is the most classically gangster movie moment he's had so far, and he quickly gets embroiled in a feud with Gyp Rosetti (Bobby Cannavale), a Sicilian hothead with the ability to perceive even the most innocent comment as a vendetta-worthy insult. (After Nucky tries to caution him to stop taking things so personally, an indignant Gyp asks, "What the fuck is life if it's not personal?")
 
But Nucky is still a character who prefers the air of respectability, and "Boardwalk Empire" battles those same impulses. At times, the show is perfectly happy to be a well-crafted bit of pulp fiction, telling bracing, violent, funny mob war stories. At others, it aspires to more artful purposes, telling stories about race, class and gender in the 1920s. It's excellent at these disparate aims, thanks to an incredible cast and a flair for crafting memorable moments and visuals, and as a result remains a must-watch in the Sepinwall household. 
 
And yet I keep waiting for "Boardwalk Empire" to cohere into something greater than the sum of its individually fantastic parts.
 
It doesn't have to go full-on "White Heat," nor does it have to ditch all the violence in favor of loftier aims. But some kind of connective tissue between the series' two sides — and between action that takes place everywhere from Atlantic City itself to Chicago (where disgraced former Prohibition agent Nelson Van Alden lives not far from Al Capone), New York (where Arnold Rothstein, Meyer Lansky and Lucky Luciano are looking to settle a beef) and Washington D.C. (where Nucky's friends in the Harding administration run into trouble) — is missing. Nucky is meant to be that glue, but he spends much of the season's first half distracted by personal business.
 
The actors all get their moments to shine, even if their stories don't always feel attached to one another. (As Fienberg noted on our podcast this week, most of the supporting actors seem to alternate episodes.) Stephen Graham gets to play a few heartbreaking scenes involving Capone and his deaf son. As Jimmy's old pal Richard Harrow, Jack Huston continues to find new micro-expressions for the half of his face you can see, even as your eyes are drawn to the lifelike mask obscuring the other half. As Nucky's progressive wife Margaret, Kelly Macdonald still adds just the right amount of sugar to the medicine she's serving the men around her, and every scene with Michael Kenneth William as black crimelord Chalky White is a pleasure. And both major newcomers to the ensemble are excellent: Cannavale finds an odd vulnerability in a character who could just be a time-lost Joe Pesci from "Goodfellas," and Stephen Root has himself a marvelous time as Gaston Bullock Means, a real-life political fixer from this era.
 
The season's first half spins a lot of story threads, and much of what I feel about the post-Jimmy version of "Boardwalk Empire" will depend on how Winter and his writers tie them all together in the second half.
 
Even though Nucky is more of a gangster than before, he hasn't completed the transformation. Nor has "Boardwalk Empire" yet taken the big creative leap I keep sensing it has inside it. But there's still time for both.
 
Alan Sepinwall may be reached at sepinwall@hitfix.com