Emil Trueheart runs a loan free Delicatessen and lives in an upstairs apartment with his wife and their daughter Tess who is dating Dick Tracy. Tracy arrives for dinner (a common occurrence) and later in the evening proposes to Tess. Outside Crutch and another hoodlum scope out the Delicatessen and observe Emil placing his life savings of $1000 into a lock box. It is revealed through their conversations that they work for Big Boy. As Tracy and Tess announce their engagement the two mugs burst into the apartment and demand the Trueheart’s money. Emil resists and is shot in the chest by Crutch, who then grabs the cash and Tess for good measure. Mamma Trueheart faints and Tracy is knocked unconscious attempting to save Tess. When Tracy wakes the police are on the scene and he vows to rescue Tess and avenge her father’s death, joining the police Plain Clothes detective department at the urging of Chief Brandon.
Having kidnapped Tess Trueheart, Big Boy attempts to win her over to his services. Meanwhile officer Milligan gets a lead on Big Boy’s gang and Dick Tracy begins his first case, going undercover as the mug “Joe Smith”. Tracy meets Ribs Mocco and his man Spike at a boarding house and they take him on as their third man of a payroll robbery. Ribs says the payroll loot will be split four ways and when Tracy asks about this he learns Big Boy takes a cut of everything in the city. Unknown to Tracy, Ribs is using him and plans to cut him out of the haul. Big Boy tells Ribs that the getaway driver will be Tess and that his men will be watching the operation to make sure she sticks to plan.Before the robbery goes down, Tracy warns Mr. Peck of the Western Company and sets a trap for Ribs and Spike. The sting goes down and both Ribs and Spike are arrested and Tracy disguises himself with Ribs cap and coat and runs to the getaway car where Tess is waiting. At first the ruse works but a gunman named Max notices that Tracy is in the car, not Mocco and opens up with his machine gun at Big Boy’s urging. A passing van shields Tracy and Tess from the hail of bullets, but they still have to deal with a chasing car. Driving dangerously, Tess and Tracy stay ahead of the hoods and just miss a train which collides with the trailing gang car. Tracy then guides Tess to the hospital where she can find her mother who has been suffering from shock.
Big Boy’s attorney Magern fixes bail and Ribs Mocco and Spike walk out of the joint hours after they were arrested. Very upset with Ribs, Big Boy smacks him around a bit and orders him to rub out Dick Tracy. Ribs sets Crutch and Spike up on street a couple blocks from the place Tracy is staying and then lets himself be seen by Dick before holding up a cabby and driving away. Tracy hails his own cab and gives chase. Ribs cabbie gets confused on directions and ends up behind Tracy. Ribs realizes the danger and urges his driver to get ahead of Tracy, but it is to late and Crutch and Spike open up on the Mocco vehicle. Ribs takes several bullets to the stomach and his cab driver is killed. Tracy returns to try and arrest Crutch and Spike and a shootout ensues. Officer Milligan and his partner arrive at the corner and pinch Crutch and Spike in crossfire where both gunmen are killed. Tracy recognizes Crutch as the man who shot Emil Trueheart and declares it a good day. Ribs Mocco would survive but refuses to rat out Big Boy while in the hospital.
Dick Tracy goes after Big Boy in his apartment with partner Pat Patton and a couple of officers. Moll Texie Garcia warns Big Boy of the arriving cops and the boss sends his men out through an escape tunnel while he has Texie play the piano to keep the cops off balance. Outside the apartment Tracy knocks on the door while Patton peaks through a keyhole. His mistake, from inside, Big Boy unloads a pistol through the door hitting Patton in the arm and grazing his eye. Handing the gun off to his moll because it will go easier on her, Big Boy escapes through the secret passage.Texie takes the blame for shooting Patton and is arrested Dick Tracy doesn’t believe Texie was the shooter and tries to get her to turn but she won’t admit to anything. A lawyer named Hy Habeas arrives, wanting to spring Texie from jail. Habeas is not the normal Big Boy lawyer, and is instead working with Dubbs the ex-politician. Tracy follows Habeas and overhears Dubbs and Habeas plan to kill Texie because she has been blackmailing Dubbs for years.Texie is released on bail and taken by Habeas. Tracy ditches Tess over Christmas trying to prevent the murder. To make matters worse, he refuses to tell her what is going on. Held by Habeas and Dubbs, Texie uses her ace card and tells the men that she sent documents to another lawyer friend who will reveal their dealings should she be killed. Both men don’t know what to do when Tracy and the police arrive. Dubbs takes his own life rather than face arrest or future blackmail while Hy Habeas and Texie Garcia escape.