"Devil You Know" is the sixth episode of the fifth season of Boardwalk Empire, and the 54th episode overall. It was written by Executive Producer Howard Korder and helmed by regular director Jeremy Podeswa. It first aired on October 12th, 2014.
Chalky runs into Narcisse in Harlem with a plan to set Daughter free. Meanwhile, Nucky mingles with a different crowd when he tries to drown his sorrows in alcohol; and in Chicago, the Feds tap Eli and Nelson to help them neutralize the Capone empire. Also: A young Nucky complains to Mabel about his endorsement of Jim Neary, and teams up with Eli to catch a thief in 1897.
Deputy Nucky is now married to Mabel and expecting their first child while trying to capture a young boy who has been thieving and peddling on the boardwalk—later revealed to be a young girl named Gillian. In the present day, Nucky drowns his frustrations and grief over Sally's death at a seedy bar, where he ends up in a drunken fight and is robbed by two women who leave him knocked out in the alley. Eli and Nelson Van Alden are forcibly held by Ralph Capone after their plan to steal the financial ledgers from Capone's office fails. Mike D'Angelo attempts to get the two out under cover of disposing them quickly and quietly with his own men, which Ralph agrees to in order to avoid upsetting the trigger temper of Al Capone. However, Al returns with visiting movie stars George Raft and Paul Muni before they can leave, and is unavoidably apprised of the failed theft. Chalky and Narcisse finally meet again after seven years, with Narcisse willingly entering the room unarmed and alone to talk to Chalky. Narcisse informs him that things are changing and the Luciano threat is rising, then offers him a position in his organization. In return for his loyalty, Narcisse will release Daughter Maitland and her child and remove the blockade he's placed to prevent anyone from playing Daughter's new record. In a private room away from the eyes and ears of the visiting actors, Capone threatens Nelson, demanding to know what he and Eli are up to. Nelson snaps and tries to kill Capone by strangulation while finally admitting to his past as a Prohibition agent, but is shot in the head by Mike D'Angelo before he can reveal that the feds are investigating Capone. A rattled Capone allows D'Angelo to take Eli to kill quietly elsewhere, and actually orders the incriminating financial ledgers given to him for safekeeping. Having gotten what he wanted, D'Angelo lets Eli go in the lobby, unconcerned with his fate, and throws a crumpled bill at his feet for bus fare. Mickey rallies an army as Nucky prepares to move against Luciano, Lansky and Torrio. Meanwhile, Daughter, afraid for Chalky's life, warns him of Narcisse's treachery when Chalky agrees to work for Narcisse, but Chalky is already aware that he will most likely betray him. Despite this, he takes the deal in order to help Daughter pursue the success and life he believes she should have, and tenderly says goodbye to her and her child, Althea —who is, he has since learned, his daughter. After Daughter leaves, Chalky is led out back, where he is unsurprised to find himself blocked off by a line of Narcisse's men, guns raised to execute him. After taking a moment to straighten his suit, he tells them he's ready, and closes his eyes with a smile and a memory of Daughter's singing in his ears.
- Nelson Van Alden - Shot in the head by Mike D'Angelo.
- Chalky White - Executed by firing squad on orders of Narcisse.
- Steve Buscemi as Enoch "Nucky" Thompson
- Kelly MacDonald as Margaret Thompson (credit only)
- Michael Shannon as Nelson Van Alden
- Shea Whigham as Elias "Eli" Thompson
- Stephen Graham as Al Capone
- Vincent Piazza as Salvatore Charlie "Lucky" Luciano (credit only)
- Michael Kenneth Williams as Chalky White
- Paul Sparks as Mickey Doyle
- Jeffrey Wright as Valentin Narcisse
- Ben Rosenfield as Willie Thompson (credit only)
- Gretchen Mol as Gillian Darmody (credit only)
- Domenick Lombardozzi as Ralph Capone
- Marc Pickering as Enoch Thompson, 1897
- Margot Bingham as Daughter Maitland
- John Ellison Conlee as Commodore Louis Kaestner, 1897
- Travis Tope as Tommy Darmody
- Paul Calderon as Arquimedes
- Louis Cancelmi as Mike D'Angelo
- Ginger Kearns as Irene
- Dagmara Dominczyk as Dinah
- Maya Kazan as Mabel Thompson, 1897
|#01 "Golden Days for Boys and Girls"||#05 "King of Norway"|
|#02 "The Good Listener"||#06 "Devil You Know"|
|#03 "What Jesus Said"||#07 "Friendless Child"|
|#04 "Cuanto"||#08 "Eldorado"|