'Boardwalk Empire' Season 3 Trailer: 'We Go To War' (VIDEO)

HBO has released a new trailer for "Boardwalk Empire" Season 3 that previews the Atlantic City bootlegging drama's new direction in the wake of Jimmy Darmody's death in last season's finale.

One of the most interesting developments is a conversation between Nucky Thompson and Richard Harrow, the late Darmody's right-hand man. "How many people have you killed?" Nucky asks him. "Do you think about anything?"

"You know the answer to that yourself," Harrow responds, making it clear he knows Nucky killed Jimmy. Could they be working together? It seems unlikely, given their history, but "Boardwalk's" ever-shifting alliances leave it within the realm of possibility.

Later in the trailer, Nucky makes an announcement that sets off the season's central conflict. "For my own piece of mind, I sell to one buyer only, Mr. Rothstein." The decision doesn't sit well with Gyp Rosetti, a New York gangster played by Bobby Cannavale, who tells Nucky he needs 500 cases of rum.

Rosetti stirs up trouble throughout the trailer, holding up a gas station, beating a cop with a club, and lighting someone on fire. "Gyp Rosetti is trouble for everyone, which makes him bad for business," Nucky says. Later, he tells Margaret, "There's no walking away. We go to war."

A few other developments stick out in the trailer: Nucky's brother Eli is out of jail, looking gaunt after serving a year on election rigging charges. And while Nucky and Margaret may be newlyweds, their marriage looks strained after she secretly sold his land holdings to the church. "The show must go on," she dryly says.

"Boardwalk Empire" premieres Sun., Sept. 16 at 9 p.m. ET on HBO.