Maxine Carroll, Joan Blondell, secretary to the mayor, waits impatiently for Kenny Williams, Melvyn Douglas, who is soon called away by Captain McGovern Clarence Kolb on police business. Maxine wastes no time trying to talk Kenny into leaving the force to start a family, setting up a tension of careers, loyalties, and affection that threads through the cases to come.
Kenny teams up with Detective Deever Don Beddoe and Lieutenant Bixler Donald MacBride to investigate the murder of a circus performer, a grisly case that unfolds with careful police work and a flash of violence. Their breakthrough comes when they track a jealous knife-thrower, whose motive and proximity reveal how danger and deception can sneak up in public shows and private lives alike. The city feels the sting of fear as the investigation tightens, and Kenny’s instinct for the truth—paired with Deever and Bixler’s experience—sharpens the pressure on a killer who thinks he’s uncatchable.
Kenny has another date with Maxine, but this time Captain McGovern insists he pick up Buck Moseby [Edward Brophy] at the jail and escort him to the penitentiary by train. Instead of heading straight to the rails, Kenny pretends Moseby is his college friend so he can keep his promised outing. The ruse brings Effie Perkins [Ruth Donnelly] into the circle, and the four of them—Kenny, Moseby, Effie, and Maxine—move from the jail to the beach, and then to a lively casino by the sea, where dancing and light talk blur into something deeper and more complicated. Maxine’s keen instincts sense something off, and she phones Captain McGovern to report what she’s observed, though the captain doubts her claims until a fresh twist in the tale tests everyone’s trust.
The truth begins to leak out when the prison warden calls to report that Moseby and Kenny have not arrived at the train, matching Maxine’s suspicions with a procedural check. The captain remains on the line with her as a tense cat-and-mouse game unfolds, and Moseby tries to flee once more, only to be halted by Kenny’s quick reflexes and firm grip. Effie faints at the news that Buck Moseby is a notorious convict and killer, underscoring how easily public perception can collide with a complicated private life.
That incident lands Kenny in hot water at a Citizens Committee meeting, where the police commissioner imposes a suspension of 60 days without pay. The city is unsettled by a spate of vicious, headline-grabbing attacks—the Phantom Slugger has been terrorizing women at random—and the committee pushes for a dramatic solution: a male officer in disguise could be the key to drawing out the culprit. The plan goes forward, and Maxine steps in with a note she slips to the mayor to suggest using Kenny in the undercover operation. The mayor and the department agree to reinstate him if he’ll go undercover, and Kenny accepts, walking a tightrope between duty and danger.
After 48 hours of anxious silence, Maxine worries about Kenny’s whereabouts, then learns that he has been spotted. When she reaches the location, the Phantom Slugger launches a brutal assault on her, knocking her unconscious, and Kenny—still wearing the disguise—engages the assailant in a tense struggle and manages to arrest him, securing a decisive victory against a criminal that had spooked the city into inaction. Kenny visits Maxine in the hospital, where she pretends to be gravely ill and uses the opportunity to coax him toward resignation, a move she believes will spare them both from a dangerous, reckless path.
The next day brings a fresh turn: the night watchman at the First National Bank has been killed in a burglary worth $25,000. The captain confronts Kenny with the news and reveals that Kenny’s resignation would only hinder the hunt, so Lieutenant Bixler—who has also staged a show of having resigned—keeps the tension high to spur further investigation. Meanwhile, Maxine and Effie are planning a wedding for noon at the mayor’s office, a symbolic moment of joy that Kenny often seems to be running late for. The captain arrives with a boast: Kenny has nabbed the burglar, Stanley [John Wray], who insists he was forced to take part in the robbery by another man. The atmosphere shifts from celebration to doubt as Kenny considers new angles and possible collaborators.
With time running short, Kenny uncovers evidence that could clear Stanley, but the plan to haul him to the prison by train still looms. The police and detectives press for a formal arrest, while the rest of the team weighs the consequences of taking Stanley off schedule. In a climactic surge, Kenny works with Maxine to trace the liquor bottle found in Stanley’s car to its purchaser, which leads them to the racetrack and the discovery of the real killer—a counterpoint to the earlier suspect, and a sharper, far-reaching conclusion to a case that blended romance, humor, and danger.
