As protestors gather outside the prison, Grady Finch waits execution after he's found guilty of the murder of a convenience store owner. The victim's son, Nathan Park, tells the reporters that all he wants is for Grady to confess. In the cell, Grady insists to his lawyer Liz that he's innocent. The warden arrives and tells him that the governor has chosen not to issue a stay of execution. Grady is taken to the execution chamber. As they rig him with the tubes for lethal injection, Grady uses his final words to insist that he didn't kill anyone. Nathan, angry, pounds on the observation gallery window and tells him to tell the truth. The executioner begins the injection process. A woman's voice that only Grady can hear says "Not yet.â€ The phone rings and a technician informs the warden and the executioner that the injection mechanism has jammed. They have no choice but to postpone the execution.
Back in Grady's cell, Liz tries to file a stay of execution since a second execution would be cruel and unusual punishment. The warden arrives to inform them that the governor has order the execution to continue before the day is up. In the execution chamber, Grady hears the woman says the same words. He faints and an alarm goes off. There's an electrical fire and the warden is forced to stop the execution and evacuate the prison.
Grady starts to wonder if there's a high power at work, and the protestors outside believe that the interrupted executions are a sign from God. However, the governor refuses to pardon and orders a new execution. This time Grady is to be executed by electrical chair. As the hood is placed over his head, Grady hears the woman again saying "Not yet." The executioner throws the switch and the entire system shorts out. Grady, still alive and well, laughs in triumphant.
Later, Liz visits an increasingly cocky Grady to tell him that the state's main witness against him has decided to recant their testimony and there will be a new trial. Grady explains that during the third execution, he actually saw the woman talking to him and shows Liz a sketch of the woman he saw: an angelic figure but with no wings. He believes that she's his guardian angel.
They go to a press conference and Grady starts talking about how there's a higher justice responsible for saving his life, and that he plans to make it his goal to make sure other innocent prisoners are freed. As they leave, Nathan emerges from the crowd with a gun. He tries to shoot Grady but his jam inexplicably jams. As the police take Nathan away, Grady invites anyone who wants to try and kill him to take their best shot.
As Grady and Liz go to court, a growing cult of followers cheer Grady on. He assures one woman that her husband on death row will get the same higher justice that he has. Inside the courthouse, Grady asks Liz to help him spread his message of a higher justice but she doesn't believe that there's anything supernatural going on.
Grady's new trial continues and the jury finds him not guilty. As they wait go outside, Grady finally admits to Liz in private that he did kill Nathan's father. Now that he realizes he can't be killed, and he's been found innocent, there's no reason to deny his guilt any more. As he boasts that he can't be killed, Liz reminds him "Not yet.â€ Confident, Grady goes out to greet his fans. As he remembers all of the failed executions, he looks up and sees workmen hauling a statue up. The rope breaks up and the statue falls on Grady, crushing him to death. The statue is a female, the woman from Grady's vision: Nemesis, the Goddess of Vengeance.