Nucky is shocked by an insurrection among his inner circle. An attack threatens Chalky's life and livelihood. Margaret deals with her son's problems. Angela vies for Jimmy's affection. Van Alden shows his wife around town.

Despite being publicly embarrassed by legal trouble, Nucky's biggest concern may be holding on to his private army in a battle for control of Atlantic City. Meanwhile, Jimmy pitches a business deal to Arnold Rothstein in New York, but may have more in common with Meyer Lansky and Lucky Luciano. Margaret draws on past experience to retrieve some valuable information, Chalky clashes with a fellow inmate, and an Irish nationalist comes to town looking for support.

The Commodore throws his weight around with the Coast Guard to disrupt the delivery of alcohol, which creates an opportunity for Owen to demonstrate his value to Nucky and a struggling casino. Meanwhile, a letter dredges up painful memories for Margaret, Nucky calls in a favor with the U.S. attorney general, Meyer and Lucky learn the price of power, and Lucy searches for ways to cure her loneliness.

During Mayor Bader's birthday party, Nucky's attorney comes up with a solution that might help Nucky in his election-rigging case. With a liquor surplus likely, Jimmy and Mickey travel to Philadelphia to search for buyers while Nucky makes a surprising deal to try and get alcohol into Atlantic City. Eli is concerned over the Commodore's ability to lead. Margaret decides to give her staff bonuses. Chalky is cornered while at work and home. Owen takes his munitions expertise and uses it. Van Alden's agents set their eyes on Mickey's warehouse. Richard lets his guard down in the name of art. And Gillian thinks of the first time she was ever with the Commodore.

After a dispute with his enemies, Nucky brings in a surprise guest speaker at a Memorial Day dedication for war veterans. Running out of options, Eli questions his allegiances, but it ends up sending him deeper into the hole. Nucky hires a new lawyer. Jimmy is taught a lesson by one of the Commodore's men that he won't soon forget. Richard decides to go hunting in the forest.

Nucky tries to set up a risky liquor delivery to Philadelphia. Later, Attorney General Daugherty sees a problem that might complicate Nucky's case. Jimmy finds a new mentor in Leander Whitlock who is the Commodore's lawyer. Margaret finally goes to confessional. Lucy continues to struggle with loneliness while Van Alden tries to settle his conscience.

Margaret has a family reunion. Owen gets even with a rival. Van Alden recognizes the hierarchy of the law. Jimmy wonders how a decision will affect the future.

In the wake of a personal loss, Nucky solicits advice on his political situation from Arnold Rothstein, while Eli remains suspicious of his brother’s actions. Nucky finds himself in the unfamiliar position of showing gratitude toward a federal agent. Angela meets a new friend at the beach, and eavesdrops on her husband’s treachery. Nelson gets a nanny. Nucky approaches Owen with an overseas proposition. Jimmy flexes his muscles, at Mickey Doyle’s expense.

Arriving in Belfast, Nucky and Owen meet with IRA leaders with a barter proposition. Meanwhile, in Atlantic City, Jimmy and his partners broker a deal with George Remus for his “medicinal” alcohol before taking a break to see/hear the Dempsey fight. Margaret frets when Emily’s illness takes a turn for the worse. Dunn Purnsley orchestrates a worker’s strike at the Ritz. Waxey Gordon takes action against Manny Horvitz in Philadelphia, and Randolph and Clifford Lathrop grill Halloran about Nucky’s past.

Undercut by Nucky, who has a new source for alcohol, Jimmy and his partners look to cultivate a new revenue stream in Atlantic City. With the peak tourist season approaching, the Commodore’s crew faces a choice in dealing with the city’s striking workers; either negotiate or fight back. Fearing that sin has led to misfortune, Margaret approaches Father Brennan with an “act of devotion.” Nucky gets a new lawyer. Van Alden faces an uncertain future. Manny Horvitz takes exception to a debt payment.

With Margaret pondering the consequences of sin, Nucky prepares her for a worst-case scenario as Esther Randolph plays out her trump cards. Jimmy revisits his college days with Angela and Gillian. Mickey Doyle chafes at sharing his liquor profits. Eli refuses to cop a plea. Nelson's past comes back to haunt him, tipping the scale in Nucky's favor.

In the season finale, Jimmy looks to make amends with Nucky, while Margaret weighs a life-changing decision.