They then repeat the process on Nicky; however, rather than knocking him out as they did with Dominick, they leave him just conscious enough to remain aware while they begin burying him. However, Nicky is a family man and he never gets angry with his family. The bosses also agree, Gaggi tells Marino to tell Nicky to handle things quieter. Frankie leads the beatdown, saying he's had enough of them. Nicky ignored the warning and started to run crime in Las Vegas.
Nicky was instructed by Ace to follow Lester and have his gang severely beat Lester, while Nicky watches. Ace made Ginger watch Lester being beaten and she was really upset. Ginger later goes to Nicky asking why Ace had to do that. Nicky states the Ace loves her very much and she should try working it out with him. However, this starts an affair between Nicky and Ginger, something which the mafia bosses do not tolerate.
Nicky's services as a hitman are called in when a businesswoman Anna Scott shows up at the casino and demands that her ex-partner gives her money. Scott sues him in court, and Green must show where he got the funding, which was from the mafia. Gaggi, furious over the outcome, sends Nicky to murder Scott. This causes police to start looking at Green as well although he had no idea of the murder. The media starts speculating whether Ace's friendship with Nicky could affect his license hearing, although he was promised a fair one from the senator.
After Nicky threatens Ace's banker, Ace tells him that he needs to calm down with the way he's been doing things. The bosses also agree, Gaggi tells Marino to tell Nicky to handle things quieter. Nicky starts showing his contempt for the Outfit and starts getting aggravated with Ace.
He also starts figuring out ways to throw off the detectives who have constant surveillance on him, such as radar and switching cars multiple times. Ace realizes what he wants to do, he wants to overthrow Gaggi and take control of everything. When Stone tells Nicky what Ace said, Nicky meets Ace out in the desert, where he angrily tells him never to talk behind his back again. The two are so angry at each other that when Ace sees Nicky, Frankie, and Dominick at a restaurant, he pretends he doesn't know him.
Out of spite, Nicky shows up ai the Tangiers, despite being banned. After Ace tells Nicky to hurry up and get out, Nicky loses his temper again, this time, on Billy Sherbert. He calls him a Jew prick and beats him with a telephone. Gaggi asks Marino whether he knows if Nicky's sleeping with Ace's wife. Marino narrates that he knew it could get Ace, Ginger, and Nicky killed if he told the truth.
So he lies, even though he puts himself in danger as well. By now, Nicky and his crew have become coke addicts and alcoholics, affecting the way they work. They start doing stupid things, like shooting up cop's houses after the police killed one of their members. Nicky is also worried that Ace will go to Gaggi and tell him about the affair.
Even though he hasn't made up his mind, Nicky tells Frankie to start getting ready to have Ace killed, if it comes to that. One night, Ace calls his home from the casino, but no one answers. When he gets home, he finds his daughter Amy tied to her bedpost, by Ginger. He finds out she's at Nicky's restaurant and quickly goes there. He goes to her table and warns her if she ever abuses Amy again he'll kill her. They get home where they argue some more, only to have Ginger return to Nicky's.
They argue in the back of the restaurant, and Ginger asks Nicky to have Ace killed. Nicky refuses, that he's been Ace's friend for 35 years. Nicky is more worried that the bosses are going to find out. In a fit of rage, Ginger attacks Nicky, and after being slapped a couple of times, is literally thrown out by Nicky and Frankie. Ace calls Billy Sherbert and asks him to come over to his house with his gun, fearing for his life.
The feds seize the casino and start going through the books. Philip Green admits he was being extorted and is willing to cooperate. While going through Artie Piscano's house, the feds find his record books, giving them all they need. Piscano becomes so upset that he drops dead from a heart attack.
They even show Ace the pictures of Ginger and Nicky, but Ace doesn't want to look at them. The Chicago Outfit is indicted with skimming the casino and they decide to murder anyone who can incriminate them. They reluctantly kill Andy Stone in fear that he may talk, although Nicky states a big reason is that he wasn't Italian.
John Nance is also killed while hiding from the feds in Costa Rica Nance's son had been busted for drugs, and the bosses were afraid he'd come out to save his son. Taking advantage of gaming laws that allow him to work in a casino while his gaming licence is pending, Sam doubles the casino's profits, which are skimmed by the Mafia before being reported to income tax agencies.
Impressed with his work, Mafia boss Remo Gaggi sends Sam's childhood friend and mob enforcer Nicholas "Nicky" Santoro, Nicky's younger brother Dominick, and trusted associate Frank "Frankie" Marino to protect Sam and the whole operation.
Nicky's volatile temper soon gets him banned from every casino in Las Vegas, so he, Dominick, and Frankie gather their own crew and engage in independent shakedowns and burglaries, instead. Sam meets and falls in love with a hustler and former prostitute, Ginger McKenna. They conceive a daughter and marry, but their marriage is made difficult by Ginger's covetousness and love for her manipulative former boyfriend, con artist-turned pimp Lester Diamond.
Lester is beaten severely by Sam and Nicky after they catch him conning Ginger out of some money. Ginger subsequently turns to alcohol. In , Sam makes an enemy in county commissioner Pat Webb for firing Webb's brother-in-law Don Ward for incompetence. When Sam refuses to reinstate Ward, Webb pulls Sam's license from the backlog, forcing him to face a hearing for his gaming license, while secretly arranging for the board to deny Sam.
Sam blames the incident on Nicky's recklessness, and the two argue furiously in the desert after Sam attempts to tell Nicky to leave Las Vegas. Meanwhile, the casino counters begin skimming money for themselves, prompting the Midwest Mafia bosses to put Kansas City underboss Artie Piscano in charge of overseeing the transactions. Piscano is unable to find the thieves, but keeps tabs on everything he knows about Las Vegas in a private notebook and rants about it in his grocery store.
The FBI, investigating a separate crime, have wired Piscano's store, and Piscano's detailed complaints, complete with names, spurs the FBI to begin investigating the casino.
Tired of her alcoholism, Sam finally seeks to divorce Ginger. Ginger then kidnaps their daughter, Amy, takes her to Los Angeles, and plans to flee to Europe with her and Lester.
Sam convinces Ginger to come back with Amy, and then scolds her for stealing his money and kidnapping their daughter. After he overhears Ginger talking on the phone about killing him, Sam kicks her out of the house, but soon relents. Ginger then approaches Nicky for help in getting her valuables from her and Sam's shared safety deposit box, and the two start an affair. Sam discovers this after finding Amy tied to her bed by Ginger, who is with Nicky at his restaurant.
Sam disowns Ginger, as does Nicky. A furious and drunk Ginger crashes her car into Sam's driveway, making a scene, and retrieves the key to their deposit box after distracting the attending police. Even though she succeeds in taking all of the money from the safety deposit box, she is arrested by the FBI as a material witness. The FBI moves in and closes the casino in Green decides to cooperate with the authorities. Piscano dies of a heart attack upon observing federal agents discover his notebook.
Nicky flees Las Vegas before he can be caught. The bosses are arrested and put on trial and decide to eliminate anyone involved in the scheme to prevent them from testifying. Among those killed are three casino executives, Teamsters head Andy Stone, and money courier John Nance.
Ginger travels to Los Angeles and ultimately dies of a drug overdose in a motel. Sam himself is almost killed by a car bomb and suspects Nicky was behind it. Before Sam can take revenge, Nicky and Dominick are ambushed by Frankie and their own crew, beaten, and buried alive in a cornfield, the bosses' having had enough of Nicky's behavior and suspecting his role in Sam's car bombing.
With the Mob now out of power, the old casinos are purchased by big corporations and demolished. The corporations build new and gaudier attractions, which Sam laments are not the same as when the Mafia was in control. Sam subsequently retires to San Diego and continues to live as a sports handicapper for the Mob, in his own words, ending up "right back where I started".
The research for Casino began when screenwriter Nicholas Pileggi read a report from the Las Vegas Sun about a domestic argument between Frank "Lefty" Rosenthal , a casino figure, and his wife Geri McGee , a former topless dancer. Argent was owned by Allen Glick, but the casino was believed to be controlled by various organized crime families from the Midwest. This skimming operation, when uncovered by the FBI, was the largest ever exposed.
Pileggi contacted Scorsese about taking the lead of the project, which became known as Casino. Scorsese and Pileggi collaborated on the script for five months, towards the end of Some characters were combined, and parts of the story were set in Kansas City instead of Chicago.