When writer Martin Gordon is shot and killed while roaming the grounds of a deserted Confederate fort in Dixon, Georgia, his sweetheart, Hattie Lee, witnesses the crime and hurries to summon help. Upon returning with her father, Judge George Lee, and her cousin, Ellamae Downs, Hattie discovers that Gordon's body has disappeared. Unknown to her, Gordon had been conducting simultaneous affairs with both Hattie and Ellamae, and later that night, Ellamae mails off a package to her former sorority sister Carol Lambert in New York. In a New York broadcasting studio, meanwhile, Carol is working with her fiancée Wally Benton, a radio sleuth known as "The Fox." Wally, who goes into spasms at the mere mention of murder, asks the producer of his show for a vacation so that he and Carol can get married and go on their honeymoon. When Carol receives Ellamae's package containing a Japanese beetle, though, the signal of a sorority sister in distress, she insists upon leaving for Georgia immediately. In Georgia, the prospective newlyweds discover that they must wait five days for a marriage license. They are met at the airport by the judge and his chauffeur, Chester Conway, who has a twin brother with a criminal bent named Lester. When Wally sees a picture of Lester, whom he helped send to jail, accompanied by a newspaper story detailing his escape from prison, he mistakes Chester for Lester and tries to arrest him, but is apprised of his error by the judge. That night, Ellamae takes Wally and Carol to the fort and there they discover a partially dug grave and Gordon's briefcase containing his notes for a history of the fort. Soon after, Corporal Lucken, the old confederate soldier who acts as the fort's caretaker, appears with his parrot, who whistles the tune of "Dixie." When Wally points out a circled passage in Gordon's notes concerning a Colonel Longfellow and the 96th infantry, the corporal replies there must be a mistake because there were only 67 regiments in the militia. Lester, meanwhile, has arrived in Dixon on the local freight train and proceeds to the judge's house, where he dons Chester's uniform. At the house, Lester spies Wally, whom he holds responsible for his arrest, and vows revenge. Later that night, Wally hears the drunken judge reciting a Henry Wadsworth Longfellow sonnet and realizes that Gordon must have been writing in code and that his notes refer to the poem. When Wally scrutinizes the poem, "The Arsenal at Springfield," he deciphers that it must be referring to something hidden in the floor of the fort and notifies Sheriff Claude Stagg of his discovery. The sheriff hurries to the house and meets Wally, Ellamae and Carol in the driveway. Chester, watching from a window, notices the sheriff drop a gold coin from his pocket, and after the sheriff drives off with Ellamae, Carol and Wally, Chester picks up the coin and examines it. At the fort, Wally uncovers a partially buried chest filled with English gold coins and concludes that Gordon must have been searching for the trunk when he was killed. As the sheriff pulls his gun on Wally and demands the treasure, Chester arrives at the fort and disarms the sheriff. He then explains that he became suspicious of the sheriff after seeing him drop the coin because he had earlier found a cache of coins in Gordon's desk drawer. Soon after, district attorney Frank V. Bailie appears and Wally, unaware that Bailie is the sheriff's partner in crime, turns the gun over to him. Double-crossing his accomplice, Bailie locks the sheriff in with the others in an airless powder cell, leaving them to suffocate. Once locked inside, the sheriff informs his fellow prisoners that Gordon is still alive and being held captive at Bailie's farm. Locating a water pipe leading to the outside, Wally finds the corporal's parrot nested inside and attempts to attach an SOS note to the bird. When that fails, Wally decides to teach the bird to whistle "Yankee Doodle Dandy," hoping that the tune will alert the corporal that something is amiss. After the bird flies off, Wally devises a smoke bomb from the sheriff's bullet cartridges. The bomb fails to have the desired effect, however, and instead blows up the pipe, sending water gushing into the cell. Awakened by the sound of the explosion, the judge and Hattie speed to the fort with Lester, who they think is Chester. As Wally and the others find themselves up to their necks in water, the judge arrives and alerts the corporal, who then struggles with the combination to the door. When the door finally swings open, a wall of water propels Wally and the others out of the cell. In the chaos, Lester knocks Chester unconscious and speeds to Bailie's farm while Wally puts the corporal in charge of the sheriff. Upon arriving at the farm, Wally overpowers Bailie after a fight. When Lester appears in the hayloft looking for the gold, he slugs the puzzled Wally, who thinks that he is Chester. After the twins become entangled in a rope pulley, Wally is confronted by one and then the other as they slide up and down the rope. Finally realizing that they are twins, Wally knocks them both unconscious and then is accosted by Bailie wielding a water-logged gun. Knowing that the gun is useless, Wally overpowers Bailie just as the police arrive to arrest the malefactors.