In the Martin Scorsese-directed premiere of this drama set in Atlantic City at the dawn of Prohibition, political boss Enoch “Nucky” Thompson (Steve Buscemi) brokers a sale of illegal booze for visiting New York gangster Arnold Rothstein, and takes an interest in a local housewife with an abusive husband. Meanwhile, World War I veteran and Thompson protégé Jimmy Darmody (Michael Pitt) meets a hoodlum from Chicago named Al Capone.
Investigating a crime which he feels has been pinned on a scapegoat, straight-arrow Agent Nelson Van Alden pays a visit to Nucky and leaves convinced that the Treasurer is "as corrupt as the day is long." Nucky quickly does damage control, enlisting his brother, Sheriff Elias Thompson, to close ranks with their underlings. Nucky discusses the upcoming election with his aging mentor, Commodore Louis Kaestner, with whom he debates the women's vote issue. Later, before heading out for a night on the town, Nucky rebukes an irate Arnold Rothstein over the phone, then meets privately with Margaret Schroeder, who asks him for help in providing for her children. As a long day ends, a traveling salesman named George Baxter, in town for a few days with an unwilling young beauty named Claudia, makes a startling discovery while on the road home to Baltimore.
An unlikely witness threatens to expose the perpetrators of the woods massacre, sending Eli – and Agent Nelson Van Alden – rushing to the hospital. As Nucky re-evaluates his relationship with Lucy, Margaret starts a new job at an upscale French dress shop at the Ritz. Chalky’s team pays a heavy price for taking over Mickey Doyle’s bootleg operation, causing Chalky to reevaluate his relationship with Nucky. After questioning Angela’s loyalty, Jimmy heads west.
In Chicago, Jimmy bonds with one of Johnny Torrio's prostitutes, Pearl, and finds himself increasingly at odds with the hot-headed Al Capone. Back in Atlantic City, Nucky looks to leverage his relationships with ambitious U.S. Senator Walter Edge as well as Jersey City Mayor Frank Hague. Eli and Chalky go to extremes to interrogate a KKK member, Lucky Luciano sets his sights on Jimmy's "wife" Margaret impresses at Nucky's lavish birthday party, while Lucy tries to protect her territory.
On the day of the annual St. Patrick's Eve dinner, Nucky deals with his jealous brother's oratory ambitions, as well as a group of disenchanted "Leprechauns." Feeling ignored by Nucky, a frustrated Margaret feeds Van Alden information regarding the whereabouts of a garage filled with barrels of beer. In New York, Arnold Rothstein worries about his involvement in the fixed World Series, while in Chicago, Jimmy copes with the aftermath of a vicious attack orchestrated by Torrio rival Charlie Sheridan.
