In the small town of Carvel, Judge Hardy and his wife Emily are eagerly anticipating the return of their son Andy, who has just received an honorable discharge from the Army after serving for two years. Soon after Andy returns home, Emily sees him looking at store window displays of wedding rings and baby clothing, and concludes that her son must be in love. Emily's suspicions are soon confirmed when the girl-crazy Andy barely notices Isobel Gonzales, an attractive young woman to whom he is introduced. Isobel, who is singing at the town's country club show, falls instantly in love with Andy, but her infatuation is not returned. Andy is preoccupied with thoughts of his college sweetheart, Kay Wilson, and looks forward to returning to Wainwright College as soon as possible to resume his romance. While attending the country club show with his parents, Andy panics when he learns that a telegram from Kay is about to be delivered to his house. Determined to keep the telegram and his romance a secret from his parents, Andy makes up an excuse to leave the show with help from a friend, who agrees to circulate a false story about a gushing water faucet at his home. Andy returns home in time to intercept the telegram, but a series of embarrassing mishaps ensue when Andy realizes that the police have turned off the water meter to the house. No sooner does Andy step outdoors in his bathrobe to switch the water back on than the front door shuts and locks behind him, leaving him stranded in the garden. Andy remains outside until moments after his parents return home and a passing police officer finds him lurking in the bushes. Though Andy tells the police officer that he lives there, the officer insists on taking him inside to confirm his story. Fearing that her son's erratic behavior is a sign that he has become blinded by love, Emily asks her husband to have a talk with Andy about the dangers of "designing women." When Andy confesses that he plans to ask his school sweetheart to marry him, his father and mother decide to follow him to Wainwright to keep him out of trouble. Soon after Andy returns to Wainwright, Duke Johnson, the president of the student council, asks him to be chairman of the freshman dance. Andy accepts the invitation, but is later disappointed when Kay tells him that she cannot be his date and that a family emergency requires that she must return home to be with Dane Kittridge, her legal guardian. When Duke learns that Andy is in need of a date, he sets him up with Coffy Smith, who is a great deal taller than Andy. Andy is initially embarrassed by the height difference, but he and Coffy soon become good friends. When Kay returns to Wainwright, she tells Andy that she has fallen in love with Dane and that she plans to marry him the following day. The news breaks Andy's heart, but he nevertheless agrees to be Kay's best man. After the wedding, Andy leaves Wainwright and returns home, where he plans a trip to South America to forget his sorrows. Judge Hardy, however, manages to persuade Andy to change his plans and return to Wainwright to complete his studies.