James M. Tolliver, known as "Jim", is an agent of the Bureau of Investigation deployed to Atlantic City in 1924 to investigate corruption within government officials in the town and its relation to Nucky Thompson, working under the personal command of the newly appointed Director of the BoI, J. Edgar Hoover. While in his destination Tolliver poses as Warren Knox, a rookie Prohibition Agent under the command of corrupt agents Stan Sawicki and his supervisor, Frederick Elliot. The character debuts in the fourth season premiere "New York Sour".
Knox is assigned to the command on Agent Stan Sawicki in Atlantic City in 1924.
Sawicki openly flaunts his corrupt business relationship with bootleggers Mickey Doyle, Nucky Thompson and Eli Thompson. He introduces Knox to them and then Nucky makes Knox leave the room. Knox speaks to Doyle's associate Elmer, who entreats him to protect his backwoods bootlegging operation from thieves. Elmer tells Knox that he has rigged his warehouse with a shotgun booby trap at the door.
Knox convinces Sawicki to take protection money from Elmer and they drive out to his warehouse together. Knox claims that he has poor night vision and convinces Sawicki to go first, allowing him to walk right into the booby trap. Sawicki is hit in the midsection by the blast and Elmer rushes out. Knox shoots Elmer in the head, killing him. Knox then enters the warehouse to pour himself a drink and then coolly tells Sawicki that he will call for help but that events have just got him shaken. Knox then stands over Sawicki as he expires. ("New York Sour")
- Stan Sawicki: Direct superior, murder victim
- Elmer Borst: Bootlegger, murder victim
- Nucky Thompson: Bootlegger
- Eli Thompson: Bootlegger, murderer
- Mickey Doyle: Bootlegger
- J. Edgar Hoover: Boss, leader of Bureau of Investigation
|Season four appearances|
|"New York Sour"||"Resignation"||"Acres of Diamonds"||"All In"|
|"Erlkonig"||"The North Star"||"William Wilson"||"The Old Ship of Zion"|
|"Marriage and Hunting"||"White Horse Pike"||"Havre De Grace"||"Farewell Daddy Blues"|