Nucky is awash in memories from pier-boy days growing up in 1884 Atlantic City, when the young Nucky caught the eye of the Commodore. In 1931 Cuba, Nucky joins Sally Wheet and, with a U.S. Senator in tow, forges ties with Bacardi Rum in hopes of Prohibition's repeal in the U.S. Working on Wall Street, Margaret finds herself in the hot seat when her boss, facing an internal investigation, decides his own future. Down but never out, Chalky seizes an opportunity to extricate himself from a difficult situation. In New York, Lucky Luciano sets in motion a bold plan that reverberates all the way to Nucky in Cuba.
Back from Cuba after a dangerous encounter, Nucky pays a visit to the now-retired Johnny Torrio, who agrees to broker a meeting with the new "Boss of Bosses," Salvatore Maranzano. In Chicago, Eli and Van Alden are tasked by Mike D'Angelo, Al Capone's new right-hand man, to recoup money lost during a federal raid by Eliot Ness. Fresh out of law school, Willie Thompson has a job interview. Rebuffed by a group of would-be financiers, Nucky dines with Tonino Sandrelli before sending a message to Lansky and Luciano. In 1884, a young Nucky deals with the death of his sister, Susan, while his father has a standoff with the Commodore.
Chalky heads in a new direction after assessing his latest partnership. In New York, Margaret finds herself in a quandary as a result of her association with Arnold Rothstein. Nucky hosts a prospective "big fish" partner from Boston. Luciano and Siegel meet with Narcisse in Harlem, promising business as usual, but encounter resistance. In 1884, young Nucky is privy to the passion of a hotel guest, and flirts with a young girl.
Facing a shared dilemma, Nucky and Margaret find common ground in Atlantic City. Luciano encounters an old adversary while meeting with Capone in Chicago. Sally Wheet makes a payment in Cuba amidst concerns of a grass-roots uprising. In 1884, young Nucky shows young Eli how the other half lives, and takes another step up the Commodore's ladder.
Chalky returns to Atlantic City with vengeance on his mind. Concerned about the ongoing threat from Luciano, Nucky arranges a meeting with Maranzano in New York. In Chicago, Eli's reunion with June takes an unexpected turn after a dinner party hosted by Van Alden and Sigrid. Capone looks to relocate his operation out of Chicago; Margaret completes a deal with Carolyn Rothstein; Nucky gets bad news from Cuba. In 1897, young Nucky looks to win over Mabel's father while asking for expanded responsibilities as deputy sheriff.
In Harlem, Chalky encounters Narcisse in hopes of setting Daughter Maitland free. Federal agents enlist Eli and Van Alden to help take down the Capone organization. Pained by a recent loss, Nucky turns to the bottle, and the company of a pair of barflies. In 1897, young Nucky vents his frustration to Mabel after endorsing Jim Neary, and roots out a young thief with Eli's help.
At war with Luciano, Nucky looks to hold onto his assets in Atlantic City. Willie and Eli become involved in Nucky's war. Maranzano meets his fate. Nucky reads Gillian's letter from the hospital. In 1897, Mabel and Nucky argue about a young runaway from Trenton, while Nucky does a discreet favor for the Commodore.
After a shakeup, Nucky looks to relocate to Manhattan from Atlantic City. Margaret impresses Nucky and a grain-company stockholder; Luciano tends to unfinished business while establishing a mob commission; Willie shares underworld details with his boss, the U.S. Attorney; Nucky visits Gillian at the hospital. In 1897, Nucky copes with a family crisis, while making a deal with the Commodore that will settle his future.