Set in 1920s, it's the story of Enoch Thompson, the treasurer of Atlantic County. Thompson was a politician and a gangster in the same time. With a lavish lifestyle, the federal government starts to take an interest in him.
Season four picks up in 1924 and Nucky (Who's spending more time in New York and its intriguing places) has new problems in the form of Valentin Narcisse (Jeffrey Wright) and FBI Agent Loren Knox (Brian Geraghty).