Judge Hardy risks his finances on a note to the newspaper owner and takes his family on a vacation, enabling his daughter and son to have romances.
Judge James K. Hardy (Lewis Stone) opposed the aqueduct project of Frank Redmond (Frank Craven) but agrees to sign his note to Hoyt Wells in order to keep Frank's newspaper going. Andy Hardy (Mickey Rooney) asks Polly Benedict (Ann Rutherford) for a kiss. The Hardys discuss where to go on vacation, and they decide on Judge Hardy's choice of Catalina. On the boat Andy sees swing dancing and meets fun-loving Geraldine Lane (Eleanor Lynn). The Hardys rent a cottage. Marian Hardy (Cecelia Parker) goes to the beach and meets lifeguard Bill Rand (Ted Pearson). Geraldine makes a date with Andy, and they kiss. Bill and Marian on a boat see flying fish. Bill tells her that he is married and separated.
Judge Hardy hooks a swordfish but loses it. Geraldine and Andy speed by. Andy asks his father for $5 but gets a lecture instead. Andy tells Geraldine that he has no money, but she will spend hers. Bill tells Marian that he is in love with her. Judge Hardy talks with Geraldine and warns Andy about her; but Andy says his father is old. Marian asks for a formal dress. At her place Geraldine tells Andy that Bill is married. Andy leaves and walks back. Aunt Milly (Sara Haden) tells Judge Hardy that Mary is going out with a married man. Judge Hardy inspects Marian's new gown. Bill asks Marian to marry after his divorce in a year. Judge Hardy waits up for tipsy Marian, who says she loves Bill.
Judge Hardy invites Bill on a family picnic and announces their engagement. They put Bill on trial, and Judge Hardy defends him. Bill admits it was a vacation romance and says he loves his wife. Bill leaves, and Marian cries. Judge Hardy tells her that we learn from trouble. Judge Hardy gets a telegram from Frank that he can't pay the note. Judge Hardy plans to leave but catches a marlin first.
Frank tells Judge Hardy that he is in deep. Judge Hardy takes his wife Emily (Fay Holden) to their old house and says they may have lost everything. Judge Hardy searches for Civil War scrip. Polly asks Andy for a kiss and kisses him. Judge Hardy has gone to the capitol, and Andy drives them to the foreclosing sale. A plane lands with Judge Hardy, who says he bought the government land with Civil War scrip by an old law. In the final scene Andy kisses Polly, proving what he learned at Catalina.
These characters with this cast would continue in several more movies that emphasize traditional family values and judicial responsibility. In this story both Marian and Andy learn important lessons with more experienced romantic partners that help their own maturing.