A Scotland Yard inspector struggles to get through a typical day on the job.

At the home of George Gideon, a chief inspector at Scotland Yard, Gideon is promising his wife Kate that he will bring home a fresh salmon for her dinner party when he receives a phone call from Herbert "Birdie" Sparrow, one of his informants. In a hurry to reach the Yard before meeting with Birdie, Gideon runs a red light and is pulled over by Simon Farnaby-Green, an earnest young police constable. To Gideon's annoyance, Simon disregards the inspector's rank and sternly issues him a ticket. After Gideon drives his eighteen-year-old daughter Sally to school, Sally realizes that she has forgotten to give him a ticket to her concert recital that night and asks Simon, who has followed them to school, to deliver it to Gideon at Scotland Yard. Upon reaching the Yard, Gideon irritably summons Sgt. Eric Kirby into his office and suspends him for accepting bribes. Gideon then goes to meet Birdie at the church in which he works as a caretaker. Before Gideon arrives, the church's vicar, Rev. Julian Small, is derided as a "sissy" by a group of street urchins. Gideon hopes to obtain more information about Kirby's bribes from Birdie, but their conversation is cut short when the inspector is called away to investigate a payroll robbery. At the scene of the robbery, the police find a tire track belonging to the thieves's car. Gideon then goes to question Kirby's wife at the lavish apartment she shares with her husband. Mrs. Kirby becomes agitated when Gideon suggests that the couple's elaborate furnishings have been purchased with her husband's ill-gotten gains and orders the inspector to leave. As Gideon walks down the corridor outside the apartment, a police officer arrives with the news that Kirby has been run down by a car and killed. When Gideon relays the message to Mrs. Kirby, she breaks down in tears. Soon after, Scotland Yard is alerted that a psychopathic killer is on his way to London from Manchester. Upon reaching London, the killer, Arthur Sayer, visits his niece, Rosie Saparelli. When Rosie leaves the flat to run an errand, Arthur sneaks up the stairs and murders her daughter Dolly. After exiting the house, Arthur drops his Manchester newspaper on the sidewalk. The paper is picked up by Simon, who follows Arthur to the washroom of a theater where the agitated killer declares he was driven to commit the murder. Later, at Scotland Yard, Simon is brought to Gideon because the young constable has been credited with cracking the case. Gideon initially does not recognize Simon, but when he finally does, instead of praising him, Gideon upbraids him for the traffic citation, causing the flustered Simon to forget to deliver the concert ticket. After Simon leaves, word comes that the tire tracks from the payroll robbery match those of the car that ran down Kirby. Soon after, Mrs. Kirby comes to Scotland Yard and tearfully admits that her husband had been associating with "shady characters." Gideon then shows Mrs. Kirby a woman's photograph they found in Kirby's locker, and she identifies the woman as her husband's consort. Meanwhile, Birdie is being pursued by two thugs who suspect him of being a police informant. While taking a break at a pub, Gideon is accosted by Birdie's drunken wife, who warns that her husband is in danger and begs the inspector to lock him up for his own protection. The thugs follow Birdie to the church, and when they begin to menace him, Rev. Small, a former war hero, overpowers them, thus earning the respect of the watching street urchins. After the woman in Kirby's photo is identified as Joanna Delafield, Gideon goes to question her, but she denies knowing Kirby. Gideon then brusquely informs her that Kirby has been murdered and leaves. Gideon next goes to interview Walker, the payroll master who was robbed. When he is shown Joanna's photo, Walker recognizes her as a recently hired employee. After an investigation into Joanna's criminal record reveals that she has been involved in several other payroll robberies, Gideon goes to her apartment to arrest her, but is met by Joanna's gun-wielding husband Paul, who claims that the robberies were justified because the money allowed him to pursue his true talent as an artist. Handing the gun to Joanna, Paul instructs her to watch Gideon while he finishes packing. While Paul flees out the back door, Gideon tells Joanna that she will hang for Kirby's murder, prompting her to lower her weapon is horror. At the end of the day, Gideon is about to go home when a call comes in about a break-in at the exclusive St. James Safe Deposit. Fitzhubert, a young aristocrat with a penchant for crime, and several of his confederates were about to break into the safe when a dowager stopped by to deposit her jewels. The dowager notified the police, who now arrive to cordon off the area. Using a bullhorn, an officer beseeches the criminals to come out peacefully, but Fitzhubert runs out firing his gun and is apprehended by Gideon. Gideon, bearing his salmon, returns home long after both dinner and Sally's concert have ended. Sally then arrives, accompanied by Simon, who used Gideon's ticket to attend the concert. Just then, Scotland Yard phones to inform Gideon that Paul has been traced to the London airport. Simon offers to drive Gideon there in his old jalopy, but along the way is stopped for a traffic violation. When Simon protests that the ticket should be forgiven because he was driving the chief inspector on an important mission, Gideon smiles.