At the offices of the New York Star , Johnny, a troubled young reporter, slumps despondently at his desk. Johnny's problems cause editor Crane Stewart to reminisce about another troubled young man he knew years earlier: Homicide detective Tony Cochrane dotes on his little son Doc, but is estranged from Martha, his unsophicsticated wife. Tony's estrangement arises from his love affair with Jill Merrill, a cold-hearted socialite. Although Tony has tried to break off their relationship, Jill keeps him ensnared with her sexual depravity. While passionately embracing at the beach one evening, Jill and Tony see a car stop along the road and hear a woman scream. When a man jumps out of the car and flees, Tony is about to give chase when Jill reminds him that his involvement would expose their illicit affair. Torn between his responsibility as an officer of the law and his desire to conceal his private life, Tony lets the man escape, even though he has beaten the woman to death in the car. The next day, Tony and his detective friend, Ole Strom, are assigned to investigate the woman's murder. The victim is identified as Elaine Blanchard, the daughter of a prominent family. At the beach, Capt. Lawrence notices a second set of tire prints in the sand and instructs Ole to make a plaster cast of the tracks, hoping that it will lead to the second car. On the list of Elaine's associates to be questioned, Tony is shocked to read the names of Jill and her husband Benjamin. After making sure that Martha will not be home for dinner, Tony returns to his garage that evening, and under cover of darkness, changes the tires on his car. The next day, Tony goes to the Merrills' house to question them. After Benjamin leaves for work, Tony charges Jill with knowing the identity of the murderer, but she refuses to divulge his name. In search of clues, Tony goes to Elaine's bank to review her canceled checks, and meets banker Douglas Loring, whom he recognizes as the man who ran from Elaine's car. After a harmless tramp is arrested for Elaine's murder, Tony begs Jill to testify that she saw Loring at the crime scene, but she refuses to cooperate. To obtain a set of Loring's fingerprints, Tony tricks him into signing a statement about Elaine and then pockets his pen. On the eve of the tramp's execution for Elaine's murder, Tony matches Loring's prints to the murderer's prints that were found in Elaine's car. After informing Jill that he has evidence that will incriminate Loring, Tony shows the fingerprints to Capt. Lawrence, who then takes them to District Attorney Halloran. Tony and the captain are stunned to find Loring at the district attorney's office, confessing that he spent the afternoon of the murder with Elaine, who was in love with him. When Loring claims that on the night of the murder he was at a movie theater with Jill, Jill conveniently arrives at Halloran's office to corroborate his alibi. After Halloran dismisses Tony's evidence, Tony, furious, accuses Jill of betraying him, and she sneers that she is having an affair with Loring. Conscious-stricken, Tony finally admits to Ole that he witnessed the murder. When Ole asserts that they need concrete proof, Tony remembers the discarded tires in his garage. Hurrying home, Tony reaffirms his love for Martha, and she embraces him in forgiveness. Tony, Ole and several police officers then proceed to the Merrill home, arriving in the midst of a party. Finding Jill alone in the kitchen, Tony arrests her, and as she reaches to caress him, she stabs him in the back with an ice pick. In shock, Tony escorts her to the waiting police, hands his badge to the captain and then collapses from his wound. Back in the present, after Stewart concludes his story, Johnny rises from his stupor and goes to the lobby of the newspaper building. When he speaks to Tony, the proprietor of the cigar stand, and learns that Tony's son Doc is a celebrated homicide detective, Johnny realizes that Tony was the subject of Stewart's cautionary tale and hurries home.