In a prohibition-era American city, Irish mob boss Liam “Leo” O’Bannon meets with Johnny Caspar, the owner of several illegal drinking and gambling establishments. Caspar suspects bookkeeper Bernie Bernbaum of leaking information, causing the odds on Caspar’s fixed boxing matches to plummet. Caspar intends to kill the bookkeeper, but Leo reminds him that Bernbaum pays Leo for “protection.” Caspar leaves in a huff with his heavy, Eddie Dane, insisting he will kill Bernie with or without Leo’s blessing. Tom Reagan, Leo’s trusted advisor, warns his boss against picking a fight with Caspar, but Leo, who is in love with Bernie’s sister, Verna, stands his ground. He offers to clear Tom’s gambling debt with a bookkeeper named Lazarre, but Tom refuses the offer. That night, Tom gets drunk and loses more money in a card game. He reunites with Verna Bernbaum, with whom he is having a secret affair. With Verna asleep in his bed, Tom answers the door to find Leo, who is fretting over Verna’s disappearance. Leo claims he hired “Rug” Daniels to follow Verna, and now Rug has disappeared too. Tom advises Leo to break up with Verna, who is a “grifter” just like her brother. At Leo’s club, The Shenandoah, a nervous bookkeeper named Mink approaches Tom, delivering the message that Bernie Bernbaum wants to see him. Tom warns Mink against mingling with Bernie, as long as he is in cahoots with Johnny Caspar’s man, Eddie Dane. Tom walks in on a meeting between Leo, Mayor Dale Levander, and Police Chief O’Doole, wherein Leo gives orders for police to raid Caspar’s clubs. Again, Tom advises against starting a war with Caspar, but Leo ignores him. Tom places a bet on a horse race with the bartender, Tad, then finds Verna in the ladies’ room. He accuses her of manipulating his good-hearted boss on behalf of her brother, but she sees nothing wrong with dating Leo to ensure Bernie’s protection. They kiss, but Verna pulls away and punches him. Tom throws his drink at her, and she saunters out of the bathroom. Bernie sneaks into Tom’s apartment, and offers to help Tom with his debts by facilitating a bet on a fixed fight. Tom agrees to consider it. Later, he visits Caspar at one of his clubs. Caspar also offers to clear Tom’s debt with a $1,500 check, in exchange for learning Bernie’s whereabouts. Tom does not make any promises, prompting Caspar to bring in his thugs, Frankie and Tic-Tac. However, police raid the club, and Tom is rescued from a brutal beating. Outside, Police Chief O’Doole complains about the needless feud between Leo and Caspar. Meanwhile, Rug Daniels, who was trailing Verna, is found dead. Tom suspects Verna of killing him, since he would have uncovered her affair with Tom. Verna denies murdering Rug and accuses Tom of being jealous. Caspar sends several men to kill Leo O’Bannon at home, but Leo outwits his attackers. At his office at the Shenandoah Club, Leo informs Tom he plans to marry Verna, and reiterates that he will not kill Bernie. Hoping to dissuade him, Tom reveals that he has been sleeping with Verna, and Leo retaliates by slugging him multiple times, sending him tumbling down a staircase into the main room. Later, Verna comes to Tom’s apartment with news that Leo broke up with her. She says that she and Tom are “about bad enough to deserve each other” and tries to persuade him to leave town with her and Bernie. Tom tells her that Bernie is no longer safe, and offers to warn him. Verna discloses Bernie’s whereabouts at the Royale Hotel. Tom seeks out Caspar, informs him he is no longer working for Leo, and discloses Bernie’s location. He also states that Bernie is in a homosexual relationship with Mink, who is known to be Eddie Dane’s boyfriend. Tic-Tac and Frankie kidnap Bernie and take him to Miller’s Crossing, a wooded area outside town. There, they give Tom orders to kill Bernie, but Tom takes pity on him when they are alone in the woods. He fires two shots into the air and tells Bernie to disappear, then calls Mink and instructs him to hide out until Caspar calms down. Tom lies to Caspar that Bernie named Mink and Eddie Dane as his true enemies, explaining that Mink and Dane were the ones who leaked the information about Caspar’s fixed fights, but Caspar cannot believe Dane would double-cross him. Meanwhile, Dane trails Tom and sees him meeting with Verna. At her apartment, Dane informs Verna that Tom killed Bernie, then fends off an attack by two of Leo’s men who were hired to guard her. As Dane defends himself, Verna escapes. That night, Bernie Bernbaum breaks into Tom’s apartment and threatens to come out of hiding if Tom does not kill Caspar in the next two days. Tom seeks out Tad, the Shenandoah bartender, and asks if any unusual bets have been made in the past couple of days. Tad names Clarence “Drop” Johnson, a dull-witted fighter who recently made a $2,000 bet. A police raid interrupts, proving that Caspar has become the most powerful gangster in town. Unwilling to believe Tom’s loyalty to Caspar, Eddie Dane insists Tom show him Bernie’s dead body at Miller’s Crossing. A distraught Tom vomits as Dane, Tic-Tac, and Frankie search the woods, but he is relieved when they find the decomposing body of a man who was shot in the face. Later, Tom goes to Drop Johnson’s apartment, elicits a confession that Bernie was behind his $2,000 bet, and sends a message for Bernie to get in touch with him. Tom finds Caspar at the mayor’s office and presents the following theory: Eddie Dane pretended to suspect Bernie was alive so he could continue to double-cross Caspar and leak tips about the next fixed fight. At home, Tom speaks to Bernie on the phone, correctly guessing that Bernie shot Mink in the face at Miller’s Crossing, and that Mink killed Rug Daniels. He demands a delivery of $2,000 at 4:00 a.m., or he will make sure Caspar knows Bernie is still alive. Outside his apartment, Tom is beaten by thugs, who have come to collect his gambling debts. Tom goes to Caspar’s home, tells Caspar that Mink has promised to come by his apartment at 4:00 a.m., and warns that Dane must be dealt with that night. Dane appears and attacks Tom, but Caspar retaliates with a fireplace tool, then shoots Dane in the back of the head. Caspar vows to kill Mink when he shows up at Tom’s apartment. Later, Verna finds Tom on the street. Believing he killed her brother, she holds him at gunpoint but cannot bring herself to shoot. At 4:00 a.m., Tom returns to his apartment building and sees Caspar’s driver outside. He sends the driver away just before gunshots are fired. Inside, Tom finds Bernie laughing over Caspar’s dead body. Tom takes the cash from Caspar’s wallet, then takes the gangster’s gun and surprises Bernie by pointing it at him. Although Bernie begs for mercy, Tom shoots him dead and drops the gun on Caspar’s body. Tom calls Tad the bartender, promises to settle his debt with Lazarre, and places a bet on that night’s fixed fight. Later, he finds Leo O’Bannon and Verna Bernbaum in the woods where Bernie is being buried. Verna rides off without waiting for Leo, and Leo happily informs Tom that Verna proposed marriage. He offers his forgiveness and asks Tom to come back to work for him, but Tom refuses and bids him goodbye.