A book salesman (Olin Howlin as Olin Howland) sells Blondie Bumstead (Penny Singleton) a set of books on child training because he has convinced her that Baby Dumplin (Larry Simms) is a child prodigy. Meanwhile, J.C. Dithers (Jonathan Hale), boss of Blondie's husband, Dagwood Bumstead (Arthur Lake), rips Dagwood for altering the plans on an apartment building the construction firm is building for Abner Cartwright (Robert Middlemass) and, to keep his job, Dagwood must get Cartwright to sign off on the changes - the latter refuses in order to escape from an unfavorable contract. Baby Dumpling, the genius, is registered at school and Daisy, accompanying him, is picked up by the dog-catcher on the way back home and taken to the pound. Daisy is adopted by Melinda Mason (Peggy Ann Garner), the crippled daughter of one of the town's wealthiest men. Baby Dumpling looks everywhere and can not find Daisy, and plays hooky from school the next day. Immediately, Blondie and Dagwood suspect kidnapping, and Dagwood learns that Melinda, also missing, was last seen playing with a little boy and a dog. Dagwood promptly heads for the Mason estate, where he is even more promptly arrested as a kidnap suspect.
When an encyclopedia salesman convinces Blondie Bumstead that her son, Baby Dumpling, is a certified genius, she rushes to enroll her little prodigy in school. Blondie's motherly concern causes the other kids to taunt Baby Dumpling, and he returns home with a black eye, vowing never to let his mother walk him to school again. Meanwhile, Blondie's husband Dagwood has his own problems at his office when Cartwright, one of his company's clients, refuses to pay for the building that Dagwood has just built for him. Cartwright's chicanery causes Dithers to fire Dagwood once again. The next morning, Dagwood, afraid to tell Blondie that he has been fired, leaves for the office, while family dog Daisy accompanies Baby Dumpling to school. While waiting for her master, Daisy is arrested by the dog catcher, and the next day, Baby Dumpling plays hooky from school to search for his lost dog. When the school principal notifies Blondie of her son's absence, she rushes frantically to the police station, where she meets Dagwood, who has been arrested for slugging Cartwright. Meanwhile, Baby Dumpling finds Daisy at the home of Melinda Mason, a rich crippled girl whose nurse bought the dog at the pound. Befriending Melinda, Baby Dumpling takes her to see his swing, and when Mr. Mason discovers that his daughter is missing, he also goes to the police station and there meets the Bumsteads. Dagwood then returns to the Mason home to look for Baby Dumpling, but the gardner mistakes him for a kidnapper and locks him in the shed. As the police surround the shed, Dagwood surrenders, and later they all converge at the Bumstead house, where they find Melinda walking and playing with Baby Dumpling. Grateful that his daughter is now walking, Mr. Mason buys Dagwood's building to use as a children's home and all ends happily.
