In 1933 Kansas City, Missouri, police Lt. Speer stops at a coffee shop. There, a repossession man looks for private eye Mike Murphy, Speer’s former partner. A short time later, Murphy arrives, followed by a second repossession man, and the two henchmen attack Murphy. Speer intervenes only after someone spills his coffee. The next day, Murphy and his secretary, Addy, lament the agency’s shortage of funds, when Murphy’s partner, Dehl Swift, arrives with enough cash to pay the bills and a month’s salary owed to Addy, plus a bonus. Swift claims he won the money betting on horse races, but Murphy is dubious. When Swift leaves, Addy gives her bonus to Murphy to make his car payment, and he kisses her passionately. Later, Swift goes to Fat Freddie’s nightclub where his girl friend, Ginny Lee, sings. Collecting a briefcase containing accounting ledgers from Aram Strossell, the bookkeeper of gangster Leon Coll, Swift plans to sell the information to Coll’s rival, Primo Pitt. Meanwhile, Murphy receives a telephone call from socialite Caroline Howley, inviting him to an upcoming party. Lt. Spear takes Addy on a date to a boxing match, which Swift, Coll, and Pitt, also attend. After the fight, Leon Coll and his henchmen accost Swift, who offers to return the briefcase for $50,000. Speer and Addy secretly follow Swift home. There, Swift encounters Pitt and two of his men, who demand the briefcase. Swift is shot, and when Pitt finds the briefcase empty, he throws Swift’s body out the window. Speer engages in a shootout with Pitt’s men, killing one of them. At the coroner’s office, Speer explains Swift’s death to Murphy. Later, Coll interrogates Murphy to see if he is in on the deal with Pitt. Following Swift’s funeral, Murphy returns to his apartment to find it ransacked, and Speer waiting for him. Speer reports that Coll’s bookkeeper, Aram Strossell, was found dead in the river, and suspects a connection to Swift’s death. Speer scares off a couple of Pitt’s men, who were tailing Murphy, while Murphy goes to Caroline’s party and they make love. Speer visits Pitt and procures a bullet from the gangster’s nine-millimeter handgun, hoping to match it to the one that killed Swift. The following day, a letter that Swift addressed to himself arrives at Murphy’s detective agency office containing a pawnshop claim check. Pitt and his henchman arrive and the gangster informs Murphy that Swift double-crossed him and he wants the contents of the briefcase in exchange for Caroline, whom he has kidnapped. Later, Addy collects a box from the pawnshop, and it contains a Croix de Guerre French military decoration and another key. Speer reports that the bullet from Pitt’s gun matches the one that killed Swift, but he needs an eyewitness, Ginny Lee, to make an arrest. Ginny Lee calls Murphy and asks him to meet her in a park. Speer apologizes to Addy that their date ended badly, and she questions whether he is romantically interested in her. Ginny Lee fails to meet Murphy at the park, but he finds a ticket to the Roxy Theatre on his windshield. Speer and Pitt’s men follow Murphy to the theatre, where he finds Ginny Lee. She says she is scared of Pitt, and Murphy urges her to call Speer. Murphy asks if Swift talked about changes in his routine and Ginny Lee mentions that he had been playing a lot of handball near his home. Outside, Murphy learns of a gymnasium in Swift’s neighborhood from a fledgling police officer. Speer follows Murphy, as Ginny Lee is pursued by Pitt’s men and struck by a car. At the gymnasium, Murphy uses the key from the pawnshop to open Swift’s locker and finds a package. He returns home, shows Addy the accounting books, and she informs him that Ginny Lee is in the hospital. Pitt telephones Murphy at his office, and the detective assures him that he has Coll’s records. Outside, Murphy is caught in a shootout between Pitt’s men and Coll’s men, but Speer arrives and intervenes. Speer chastises his former partner for not alerting him when he found Ginny Lee, and follows Murphy to Pitt’s headquarters. Murphy wires the briefcase holding Coll’s ledgers with explosives, but before an exchange can be made, a gun battle breaks out. Speer shoots Pitt, and he and Murphy learn that Caroline is being held at a brothel. Meanwhile, Coll’s men kidnap Addy. Speer and Murphy infiltrate the brothel to rescue Caroline. Outside, Coll demands the briefcase with his accounting records in exchange for Addy. Speer reluctantly agrees, but as Coll drives away with the briefcase, his car explodes. Later, Murphy and Caroline, and Speer and Addy, go to Fat Freddie’s nightclub to see Ginny Lee perform. Murphy suggests that he and Speer make a good team, but his former partner insults him, and the two men step outside to fight.