Martin Vail, a prominent and cynical defense attorney in Chicago, thrives in the limelight, utilizing his legal acumen to secure freedom for his high-paying clients through clever technicalities. One day, he is drawn to a news report about the arrest of Aaron Stampler, an altar boy plagued by a stutter, who stands accused of murdering the Archbishop Rushman, a revered figure within the Catholic community. Seizing this opportunity, Vail eagerly agrees to represent Aaron pro bono.
Initially, Vail’s interest lies mainly in the publicity this sensational case could yield. However, during their meetings at the county jail, he starts to believe in Aaron's innocence, despite the skepticism of Janet Venable, the prosecutor, and Vail's former romantic partner, portrayed by Laura Linney. Vail theorizes that Aaron may possess a split personality, allowing a more aggressive persona to take hold and commit violent acts.
As the murder trial unfolds, Vail uncovers a conspiracy involving influential civic leaders who have suffered significant financial losses due to the Archbishop’s decisions to withhold certain church lands from development. The Archbishop had been threatened with death over this matter, and disturbing rumors circulate that he had sexually abused young altar boys, including Aaron.
Introducing this evidence might rally the jury’s sympathy towards Aaron, yet it simultaneously suggests a motive for the crime, which the prosecution has been desperately lacking. The odds seem stacked against the defense, with substantial evidence portraying Aaron as the perpetrator, including his frantic escape from the crime scene, clothed in blood. Public sentiment runs high against Aaron, while many refuse to accept the dark truths surrounding the Archbishop.
In a daring move, Vail infiltrates the Archbishop’s apartment, discovering a pornographic videotape that implicates the Archbishop in heinous acts with altar boys and a girl named Linda. Understanding its implication, he anonymously submits the tape to Janet, expecting her to use it as crucial evidence, even when John Shaughnessy, the District Attorney, insists on suppressing these damaging revelations.
When Vail confronts Aaron about the tape, the young man breaks down, only to reveal a darker, malevolent alter ego named “Roy,” who confesses to the murder due to years of abuse at the hands of the Archbishop. This transformation shocks Vail as “Roy” physically assaults him, after which Aaron returns to his usual demeanor, appearing unaware of the outburst. Molly Arrington, the psychiatrist examining Aaron, theorizes that his multiple personality disorder stems from childhood abuse, which was triggered by the trauma he endured from the Archbishop.
As the trial progresses, Vail subtly weaves hints of the Archbishop’s true character and Aaron's psychological turmoil into the courtroom dialogue. While searching for Linda, he discovers her decomposed body but lacks hard evidence tying Aaron to her death.
At the peak of the trial, Vail places Aaron on the witness stand, skillfully probing into the boy's troubled past. However, during a heated cross-examination by Janet, Aaron suddenly transforms into Roy, physically threatening her and invoking chaos in the courtroom. Amidst the chaos, the judge decides to dismiss the jury and shift to a bench trial. Ultimately, Aaron is declared not guilty by reason of insanity, resulting in his commitment to a maximum-security mental facility. However, Janet pays the price for the scandal, as she is dismissed from her position for exposing the Archbishop's misdeeds.
In a gripping finale, Vail visits Aaron in his cell to share the news of his acquittal. To Vail’s shock, Aaron claims to remember none of the courtroom incidents; however, just as Vail turns to leave, Aaron cryptically conveys a message to Janet that hints at his awareness of everything that transpired.
> “Tell Miss Venable I hope her neck is okay,”
This revelation leads Vail to realize that Aaron has been feigning his insanity. With a chilling grin, Aaron admits to being the true architect of his alter egos and confesses to the murders, including that of Linda. Disillusioned and angered that he fell for Aaron's facade, Vail exits the courthouse, feeling a darker sense of shame and frustration, leaving the public spotlight behind as Aaron/Roy taunts him from within the cold confines of his cell.
