Sam "Ace" Rothstein, played by Robert De Niro, is a talented sports handicapper and mob associate tasked with managing the Teamsters-funded Tangiers Casino in Las Vegas, a responsibility bestowed upon him by various Midwest mob families. Utilizing lax gaming regulations that permit him to take charge while awaiting his gaming license approval, Sam swiftly assumes control of the casino, remarkably doubling its profits. These earnings are skimmed off by the Mafia before they are ever officially recorded, ensuring the bosses are satisfied with his results.
To bolster his operations, the mob sends Sam's childhood friend, Nicholas "Nicky" Santoro, an enforcer and caporegime, along with his crew to protect both him and the casino. However, Nicky's volatile nature soon turns him from an asset into a liability. His aggressive behavior gets him blacklisted from casinos, which creates further complications for Sam's already precarious situation. Ignoring the mob's rules, Nicky starts executing unauthorized shakedowns and burglaries, which undeniably upsets the balance of their operation.
In his personal life, Sam becomes infatuated with a beautiful hustler named Ginger McKenna, portrayed by Sharon Stone. Despite her reservations, they soon have a daughter named Amy and enter into marriage. Unfortunately, their relationship takes a turn for the worse when Sam discovers Ginger giving money to her former lover, a con man by the name of Lester Diamond. This betrayal intensifies the tensions as Sam clashes with Clark County Commissioner Pat Webb, complicating matters further when he fires Webb’s incompetent brother-in-law from the casino.
Webb retaliates against Sam, causing trouble with his casino license, while hidden motives to sully Sam’s reputation unfold. Undeterred, Sam takes to television to accuse the local government of corruption, drawing the ire of the mob bosses, who urge him to step back. Instead, he attributes his troubles to Nicky’s reckless actions, which leads to an explosive confrontation between the two in the desert.
As the mob’s stomach-tightening grip on the casino sits perilously on the brink, an appointed overseer, Artie Piscano, fails to conceal incriminating evidence of their operations. Meanwhile, Sam's patience wears thin as Ginger's reckless behavior and substance abuse spiral out of control. When she becomes entangled with Nicky as they collaborate to claim a portion of their combined fortune, the stakes skyrocket, putting both their lives in jeopardy.
Eventually, the empire Sam worked so hard to establish crumbles as law enforcement closes in on their illicit activities. Personal tragedies strike as Ginger succumbs to a drug overdose while the mob executes a ruthless plan to eliminate anyone who could testify against them. In a harrowing twist, Sam narrowly escapes death from a failed assassination attempt, only to learn that Nicky has met a violent end at the hands of his former allies.
With the mob obliterated, the once-vibrant gambling scene of Las Vegas is replaced by gaudy corporate establishments that prioritize profit over the charm of old-school gaming culture. Sam mourns the loss of the Las Vegas he once knew, a city that catered to the players with a sense of dignity and class. In a poignant closing moment, we see an older Sam, back in San Diego, returning to his roots as a sports handicapper, reflecting on the cyclical nature of his life, stating, > "…right back where I started."
