Mitchell Y. "Mitch" McDeere graduated from Western Kentucky University with a degree in accounting, passed his Certified Public Accountant exams on the first attempt, and graduated third in his class at Harvard Law School. Mitch is married to his high school sweetheart, Abby Sutherland, an elementary school teacher who also attended Western Kentucky University. His older brother Ray is imprisoned in Tennessee, and his other brother, Rusty, died in Vietnam.
Mitch spurns offers from law firms in New York and Chicago in favor of signing with Bendini, Lambert and Locke, a small tax law firm based in Memphis. He finds the firm's offer—a large salary, a lease on a new BMW automobile and a low interest mortgage on a house —too generous to resist. Soon after he joins, his new colleagues help him study and pass his bar exam—the first priority for new associates. Mitch is assigned to partner Avery Tolar, the firm's "bad boy," but a highly accomplished attorney.
Two of Mitch's colleagues, Marty Kozinski and Joe Hodge, die in a scuba diving accident in the Cayman Islands a few days before he starts at the firm. On his first scheduled day of work, Mitch attends their funerals. Mitch finds the deaths unsettling, but focuses on his goal of becoming the youngest partner in the firm's history. During a memorial service at the firm for the two deceased attorneys, Mitch notices plaques commemorating three other attorneys who died while working at the firm. Suspicious, he hires a private investigator, Eddie Lomax, an ex-cell mate of his brother Ray, to investigate the deaths of the attorneys.
Lomax discovers that the other three deceased attorneys died under suspicious circumstances: in a car accident, a hunting accident and a suicide, respectively. While the details of their deaths don't add up, nothing concrete was ever proven. Lomax cautions Mitch to be careful. Soon after delivering his report to Mitch, Lomax is murdered.
Shortly after Mitch passes his bar exam, Wayne Tarrance, an FBI agent, confronts Mitch. Mitch gradually learns from the FBI that the firm is part of the white collar division of the Morolto crime family of Chicago. The firm's founder, Anthony Bendini, was actually the son-in-law of old man Morolto. He founded the firm in 1944, and for almost half a century it has lured new lawyers from poor backgrounds with promises of wealth and security. Although all of the work Mitch has done so far is very real, the partners and senior associates are actively involved in a multimillion-dollar tax fraud and money laundering scheme that accounts for as much as 75 percent of the firm's business.
The firm is heavily involved in laundering money from the Moroltos' gambling and drug-dealing operations by using it to start corporations, which buy up property and businesses around the world. By the time a lawyer is aware of the firm's actual operations, he cannot leave. By the time he retires, he is too compromised to talk. No lawyer has escaped the firm alive; the five who tried to leave did so after finding out about the firm's ties to organized crime and were killed to keep them from talking. Kozinski and Hodge were actually in contact with the FBI at the time of their murders. The takedown of the Moroltos is such a high priority that the FBI's director, F. Denton Voyles, is personally involved in the case. Mitch learns that his house, office and car are bugged. Mitch and Abby are also routinely followed by Morolto goons, making his meetings with the FBI dangerous. Pressure from the FBI, which warns him he will almost certainly go to prison if he chooses to ignore them, as well as the firm forces Mitch to make a decision quickly.
Desperate to find a way out and stay alive in the process, Mitch and Abby secretly decide to flee the country after they turn over enough evidence to destroy the firm, since they don't completely trust the FBI to protect them. In order to cooperate with the FBI, Mitch must disclose information about his clients. The attorney–client privilege in most U.S. states, including Tennessee, does not apply to situations where a lawyer knows that a crime is taking place. However, Mitch has to disclose information about some of his legitimate clients as well—which will all but end his legal career. He promises to collect enough evidence to bring down the firm in return for $2 million and Ray's release from prison.
Working with Lomax's secretary and lover, Tammy Hemphill, Mitch obtains several confidential documents from the firm's bank records in the Caymans, eventually copying over 10,000 documents detailing over 20 years of illegal transactions. He then tells Tarrance that while these documents spell out only a fraction of the firm's illicit activitiess, they contain enough evidence to indict roughly half the firm's active members and several retired partners right away. However, the documents will also provide strong circumstantial evidence that the firm is part and parcel of a criminal conspiracy. This will give the FBI probable cause to obtain a search warrant for the firm's building in downtown Memphis—and with it, access to all of the firm's dirty files. Mitch is certain those files will provide enough evidence for a massive RICO indictment that will bring down the firm and cripple the Morolto family.
Meanwhile, the firm becomes suspicious of Mitch. Tarry Ross, alias "Alfred," a top FBI official and close confidant of Voyles who is actually a mole for another crime family, confirms that Mitch is indeed working with the FBI. Once Mitch learns of the leak, he flees to Panama City Beach, Florida both the FBI and Mafia with his brother and wife. On the way, he steals $10 million from one of the firm's Grand Cayman bank accounts, sending some of the money to his mother and in-laws, storing some in a Swiss bank account and leaving the rest for Tammy.
Mitch manages to escape to the Caymans with the help of Barry Abanks, a scuba diving business owner whose son died in the incident where the Moroltos killed Kozinski and Hodge. Armed with Mitch's evidence, the FBI indicts 51 present and former members of the Bendini firm, as well as 31 alleged members of the Morolto family, for everything from money laundering to mail fraud. At the end, Mitch, Abby, and Ray are quietly enjoying their newfound wealth in the Caymans.