On the last day before Prohibition, Nucky Thompson condemns alcohol before a temperance group and later tells his ward bosses his plan for bootlegging.
Agent Nelson Van Alden visits Nucky as he probes a crime he believes his suspect didn't commit; Nucky calls his brother, the sheriff, to circle the wagons.
Nucky, Federal Agent Nelson Van Alden and gangster Arnold Rothstein each try to get to a hospital patient who knows about a multiple murder in the woods.
Jimmy Darmody visits Al Capone in Chicago and finds they have different ideas of how to run a business; Nucky tries to get more roads built to Atlantic City.
Nucky gets tough with Lucky Luciano after one of his ward bosses is robbed; Margaret stands up to the owner of the dress shop and then accepts help from Nucky.
Nucky has his childhood home redone after his father is hurt in a fall; Chalky White considers a supplier's offer that would allow him to bypass Nucky.
Nucky travels to Chicago to attend the 1920 Republican National Convention and while he's there, he gets bad news from Atlantic City about a potential gang war.
Nucky asks Margaret to stay loyal to his side; Jimmy's violent side takes Angela by surprise; Agent Van Alden's emotional conflicts interfere with his work.
Nucky makes some big changes to shake things up; Jimmy is beset by family problems; Van Alden has a stern discussion with Agent Sebso about his temptations.
Nucky is shocked to find that some of those he trusts are considering rebellion; an attack endangers Chalky; Margaret tries to deal with her son's behavior.
As tensions with the commodore increase, Nucky tries to find relief by calling in a favor; a man tries to prove his value; Lucy combats her loneliness.
Nucky surprises everyone with his guest speaker at a dedication; desperation causes Sheriff Thompson to question his loyalties; Jimmy is taught a lesson.
Nucky arranges a delivery in Philadelphia; the attorney general encounters a dilemma that may cause complications for Nucky's case; Jimmy befriends a lawyer.
Jimmy faces a choice that has lasting consequences; Margaret sees her family; Nelson puts his trust in a new prosecutor; Owen plans to get even with someone.
Nucky changes the course he is on after listening to Arnold Rothstein's advice; Jimmy elects to show off his power and picks Mickey Doyle as his target.
In Ireland, Nucky attempt to come to an agreement that will benefit both parties, while Jimmy express interest in a supply of alcohol back in Atlantic City.
Jimmy and his partners look for a new source of revenue; the commodore's men devise a plan to deal with the strike; Margaret tries to absolve her sins.