In 1890 in southern Florida, postal carrier Steven Pierton evades beachcombers and alligators as he makes his way on foot between the rugged coastal towns of Miami and Palm Beach to retrieve the mail. The Palm Beach mail boat brings in passengers, among them dandy Sylvanus Hurley from New York and pigtailed young Adie Titus. At the town trading store, Sylvanus inquires about transportation to Miami, and impresses the locals, including a beachcomber, Theron, with a wad of money and his extravagant plans to invest in the land around Miami. Steve then details the attempted attack by the beachcombers and accuses Theron of being their ringleader. A fight breaks out that Sylvanus helps quell. He then asks to accompany Steve on his walk back to Miami, employing the protection of the U.S. Mail by sending his money to himself. Adie pleads to accompany the men, but they refuse and put her in the care of Mrs. Thomas. Later that evening, Mrs. Thomas is startled to find adult clothing in Adie's bag, and Adie confesses that she is actually nineteen years old, but has to masquerade as a child as she is traveling alone. The next day, Adie follows Steve and Sylvanus on their way to Miami, but is quickly found out. When Sylvanus realizes Adie's secret, he delightedly agrees to allow her to continue with them. That night, Steve accidentally espies Adie in her undergarments and, distressed, advises her to remain in disguise to avoid danger from the marauding beachcombers. The journey resumes with a dangerous crossing of the alligator-infested river, but the trio is then waylaid by Theron and the beachcombers, who knock out the men and seize Sylvanus' envelope and Adie. Upon reviving, Sylvanus continues to Miami for help while Steve follows the beachcombers. In Miami, Sylvanus rounds up Adie's uncle Ben and several men at Dan Paget's trading post. At the beachcombers' headquarters, Steve watches as a quarrel breaks out when the men realize Sylvanus' envelope is empty, as he has hidden the money in his hat. Adie uses the diversion to dart away with Steve, and the gang gives chase before Sylvanus and the Miamians come to the rescue, arresting the beachcombers. Later in Miami, Paget, who is also the town mayor, examines a property deed Sylvanus produces. Upon showing Sylvanus the deed's worthless swampland, Paget, sensing Sylvanus' designing nature, suggests a plot by which they can convince the gullible townsfolk that the railroad is coming to Miami, bringing prosperity. In town, Sylvanus casually drops remarks that lead the townspeople to believe the railroad story, and when Ben expresses worry about rampant land speculation, he suggests they incorporate. Paget offers to be a partner in the land corporation and Sylvanus, at the insistence of the town, is made treasurer. On the night of a big dance, Adie is dismayed when Sylvanus tells her he is going north to purchase equipment for his property, and is unaware that he intends to flee with the corporate funds. As Steve and Sylvanus engage in a dance contest over Adie, Paget helps Theron and his gang break out of jail and stage a robbery of his store, taking guns and, apparently, the corporation money. The gang proceeds to go on a rampage of the town before meeting Paget, who has agreed to give them a cut. Steve goes to Palm Beach for help, while Sylvanus tries to convince Adie to leave with him. Theron, wanting Adie for himself, reveals Sylvanus' complicity in the corporation scheme in front of Adie and the town. Although angered, Adie follows Sylvanus' request to get Steve when Sylvanus is taken hostage by the beachcombers. Crossing the river alone in a small boat, Adie is attacked by several alligators before Steve, returning with a state marshal, saves her. As a barge carrying the lawmen from Palm Beach crosses the river, Sylvanus frees himself and warns them of the gang's intended ambush. Because of his help, no charges are brought against Sylvanus, and in gratitude he gives Steve and Adie his land deed. As he departs Miami for Cuba, he then reads in a newspaper article that the railroad is coming to southern Florida.