A cop enforcing ordinances strictly causes a man to go to prison but learns the value of kindness and human compassion.
New York Police Captain Cromwell (Donald Crisp) complains to reporter Pinky Holden (Hobart Cavanaugh) about his O'Malley story. James Aloysius O'Malley (Pat O'Brien) enforces petty ordinances, and a judge calls Captain Cromwell, who tells O'Malley to be a peace officer with a heart. O'Malley tells his mother (Mary Gordon) not to throw crumbs to birds. O'Malley gives John Phillips (Humphrey Bogart) a ticket to fix a muffler, and Phillips loses a new job for being late. With a wife and child Phillips tries to pawn his medals and gun but is offered only $3. Phillips knocks out the pawn broker and robs the cash register. O'Malley stops Phillips for his muffler.
In court Phillips' lawyer (Henry O'Neill) explains how O'Malley caused Phillips to lose his job, but Phillips is sentenced to 2-10 years. Cromwell urges O'Malley to resign and assigns him to school-crossing duty. O'Malley lectures children and warns Judy Nolan (Ann Sheridan) about the aisles. O'Malley helps crippled Barbara Phillips (Sybil Jason), gives a man a ticket for blowing his horn, and argues with Judy. Barbara shares an apple with O'Malley, who makes a paper crown for her on May Day. O'Malley saves Barbara from a truck, and he and Judy take her home. O'Malley gives Judy money to buy groceries and learns that Barbara's father is John Phillips. Mrs. Phillips (Frieda Inescort) comes in and blames O'Malley. Judy tells O'Malley that he is not human.
Barbara can't play because of her leg, and O'Malley goes to Dr. Larson (Frank Reicher), who says he will treat her for free. Judy and Father Patrick (Frank Sheridan) tell Mrs. Phillips. After the operation O'Malley visits Barbara. O'Malley goes to the factory to get Phillips a job and asks the board to parole Phillips. In prison Phillips is told that ex-cons have no chance hounded by cops. Phillips gets out and is told by several people that O'Malley wants to see him. O'Malley brings presents for Barbara, who thinks her father was in Canada. O'Malley asks to talk with Phillips, who in fear shoots him. In the hospital Cromwell asks O'Malley who shot him, but he is delirious. Cromwell tells Phillips what O'Malley did for him. O'Malley says it was an accident, and Phillips gives blood for O'Malley's transfusion. In the final scene O'Malley goes back to his old beat and is kind now.
This compassionate drama shows how zealous police can either make people miserable or temper justice with mercy by being understanding and helpful.