Newspaper publisher Austin Spencer, an advocate of abolishing capital punishment, invites his former employee, novelist Tom Garrett, to witness an execution orchestrated by district attorney Roy Thompson. At a bar afterward, Austin explains that he is concerned that Thompson, who wants to become governor, is repeatedly using circumstantial evidence to win the death sentence in order to create publicity. That night, Tom proposes to Austin’s daughter Susan, and she gives him an engraved cigarette lighter as a gift. She wants to announce the wedding date, but after Tom receives a phone call, he informs her that his editor insists that he finish his novel immediately. Although Susan is upset about the postponement, she agrees to wait to marry. Later, Tom discusses capital punishment with Austin as a possible topic for his novel. Austin, who wants to prove that the legal system is too flawed to allow execution as a possible punishment, suggests that they find an unsolved crime, plant evidence that will condemn an innocent man, then finally reveal that the evidence was falsified. Soon after, Austin reads that an exotic dancer, Patty Gray, has been strangled, and convinces Tom, in order to use the details for his novel, to position himself as a possible suspect. First, Austin learns details about the case from a police detective, including the fact that Patty’s fellow dancers, Sally Moore and Terry LaRue, saw her drive away the night of her murder with a man in a gray coat smoking a pipe, driving a dark sedan. Six days later, when no further clues have been found, Tom and Austin begin their scheme, agreeing not to inform Susan so she cannot reveal anything to the police. Tom makes Sally’s acquaintance by first spilling a drink on her and later visiting her at the club with money for her cleaning bill. The rough Sally is so thrilled to have a wealthy suitor that she fails to notice when Tom steals her body makeup. Soon, Susan spots a photo of Tom and Sally in the newspaper and questions him about the affair, stating that she does not mind a fling but cannot bear him lying to her. Tom urges her to trust him, but when he refuses to clarify his relationship with Sally, Susan breaks off their engagement. Tom and Austin then visit the scene of the crime, where Austin photographs Tom leaving his cigarette case as a false clue. That night at the club, Terry notes Tom’s gray jacket and dark car and worries that he may be Patty’s killer, prompting Sally to inform police lieutenant Kennedy about her upcoming date with Tom. Meanwhile, as Austin photographs his activities as proof of his innocence, Tom cleans his car of all fingerprints, applies body makeup to the interior and leaves a stocking in his glove compartment. When Tom takes Sally out that evening, the police follow him, and upon seeing him harass Sally, arrest him. The police interrogate Tom for hours, during which he answers their questions truthfully. When he is indicted for murder, Susan urges Austin to intervene, and finds her father’s nonchalance shocking. Thompson is eager to try the case in court, but his assistant, Bob Hale, is in love with Susan and hopes to help her prove Tom’s innocence. At the trial, Thompson emphasizes Tom’s coat, car and the lighter found at the scene. He conjectures that Tom, who proposed to Susan five days before Patty’s murder, killed the dancer in order to conceal his past affair with her. As “evidence,” he points to a large cash withdrawal Tom made from his bank on the same day that Patty went to work flaunting a large wad of cash, as well as pipe residue found in Tom’s garage, despite Tom’s insistence that he does not smoke. As the jury deliberates, Austin gathers his photographs and heads to Thompson’s to reveal the ploy, but along the way is hit by a car. The explosion burns his body and the photographs. When Tom hears about Austin's death, he tells the true story to his lawyer, Jonathan Wilson, who notifies the judge. Without new evidence clearing Tom, however, the judge cannot stop the proceedings. Susan and Jonathan search Austin’s safe for the photographs, but find none, prompting Susan to guess that they may have been burned in the car. When the police recover charred remains of photographs, Susan is completely convinced of Tom’s innocence, and attempts to use her influence over the newspaper editors to sway public opinion in Tom’s favor. No pardon can be granted, however, and the night before Tom’s scheduled execution, Susan implores Bob to investigate further. He discovers that Patty, whose real name is Emma, stole money from a boyfriend who then threatened to kill her. Although Susan is thrilled by this revelation, Thompson soon learns that the boyfriend died years earlier. Just then, a probate lawyer arrives at Thompson’s office with a just-discovered note that Austin left in his safe-deposit vault. The letter corroborates Tom’s story and clears him of guilt. As the governor arrives to pardon Tom, Susan meets with Tom, and when he calls Patty “Emma,” she realizes that he knew the dancer all along. Trapped, Tom admits that he killed Patty, an ex-wife who refused to allow him a divorce. Susan races home, and soon after, Bob visits. Although she tries to be brave, she breaks down and reveals Tom’s secret to him. The governor is just about to sign Tom’s pardon when Bob calls with the truth, and a horrified Tom is led back to his cell.