Season Three Premiere. Nucky makes a New Year's resolution that does not sit well with Gyp Rosetti. Margaret looks to build on the Thompson endowment at St. Theresa's Hospital. Gillian builds a new business. In Chicago, Al Capone is rankled by Irish mobster Dean O'Banion, and Van Alden stumbles onto a confrontation that could change his career path.
Mixing business with pleasure in New York, Nucky bristles at the collection tactics of Gaston Means, a 'special investigator' with ties to Daugherty. Margaret's altruism is met with resistance; Gyp makes a power play in Tabor Heights; Chalky and his daughter fail to agree on her future with Samuel; Eli gets a new boss; a major liquor shipment is detoured.
Nucky reluctantly joins Margaret to receive a high honor from the Church. Meanwhile, Gyp makes a deal with Nucky for a one-time liquor shipment. Van Alden regrets trying to socialize with his co-workers; Margaret takes her pitch to a higher authority; Lucky and Meyer protect their investments; Richard sets the record straight with Mickey, and with Nucky.
After tracking down a liquor thief, Nucky and Owen end up spending a long night hiding out from the Feds with the precocious perp. In his boss' absence, Mickey makes a routing call that will have far-reaching consequences. Margaret encounters a familiar face while promoting Dr. Mason's classes at the new woman's clinic. In Chicago, Capone's feud with O'Banion heats up.
After venting with Nucky about his liquor travails, Rothstein sends Gyp a message. In Washington, Gaston Means sees opportunity in a Senate investigation of Harry Daugherty and the Justice Department. Van Alden and Sigrid receive an unexpected visitor; Gillian worries about keeping her business afloat; Margaret has awkward moments at the hospital and at Madam Jeunet's.
After being detained in Washington by Daugherty's men, Nucky approaches his onetime nemesis, Esther Randolph, and later entertains an intriguing proposition from Gaston Means. In Atlantic City, Margaret copes with Teddy's demons while Owen investigates a suspicious fire; Gillian feuds with Lucky and finds a surrogate for Jimmy; and Richard connects with a vet and his daughter.
On Easter Sunday, Eli looks to get back in Nucky's good graces at a Thompson family reunion. While Richard and Tommy spend the day as guests of the Sagorskys, Gillian stays at home and makes a sacrifice to improve her future. In New York, after dinner and prayers, Gyp heads downtown in search of a blessing--from Joe Masseria.
Gillian makes her peace with Jimmy's death, though not with Nucky, as Gyp arrives to play ally. Working off his debt to O'Banion, Van Alden attends a meeting with Capone and Torrio; Nucky pays an unscheduled visit to Andrew Mellon; Margaret makes a stand on birth control; Nucky and Owen shop for a birthday pony; Billie eyes a future on the silver screen, to Nucky's chagrin.
Reeling from Gyp's most recent attack, Nucky vows to eliminate his nemesis through a coalition of familiar partners. In Washington, the arrest of a bootlegger puts Daugherty and Jess Smith on the hot seat. Emily gets a scaled-down birthday party; Gillian blames an absent Harrow for Tommy's latest misadventure; Gyp decides to buy a town's silence; Broadway mourns a fallen star.
Nucky reaches out to Gaston Means to keep Jess Smith quiet in Washington, and enlists Owen to neutralize Gyp's alliance with Joe Masseria in New York. Margaret considers an alternate future; Van Alden's side business backfires; Gyp fumes when a shipment comes up short; Harrow coerces an apology for Julia; Chalky sees opportunity in the ashes of a boardwalk institution.
Gyp makes his move in Atlantic City, forcing Nucky and Eddie to seek refuge with Chalky. With the Artemis Club overrun by Rosetti thugs, Gillian contemplates a business future that includes an unwelcome partner. Luciano makes a deal he'll come to regret; Harrow loses his house privileges.
Season Three Finale. Desperate to weaken Gyp's alliance with Masseria and reclaim Atlantic City, Nucky cedes control of a prized asset to Rothstein. Harrow returns to Gillian's brothel for some unfinished business; Luciano is forced to take on a new heroin partner; Chalky and Capone team up; Margaret ends one relationship and considers resuming another.