As he is about to sail from Veracruz, Mexico, Duke Halliday is confronted at gunpoint by Capt. Vincent Blake. While Blake is searching Duke's luggage, however, Duke knocks him out and steals his identification papers. Duke then shoves his way through a crowd and is chastised for his rude behavior by disembarking American Joan Graham. Leaving Duke at the pier, Joan finds Jim Fiske, her double-crossing fiancé, in a hotel room and demands that he return the $2,000 he "borrowed" from her. The smooth-talking Fiske promises to return the money as soon as he makes a paid delivery, but while Joan is taking a shower, he slips out with the valuables. Duke then walks into the room looking for Fiske and identifies himself to Joan as Capt. Blake. Feigning nonchalance, Joan dismisses Duke, but then finds Fiske in the hotel garage and tells him about Duke's visit. Just then, Duke appears and begins fighting with Fiske. Fiske gets away, and Duke and Joan are brought to the local police station. Once again Duke identifies himself as Blake and tells Inspector-General Ortega that he is pursuing a fugitive. The amiable Ortega allows Duke and Joan to go their separate ways, but immediately orders a tail put on them. Soon after, Blake shows up in Ortega's office, explaining that Duke stole his papers and is wanted for extradition to the United States. As with Duke, Ortega seemingly accepts Blake's story, then heads for the airport. Joan, meanwhile, is driving toward Tehuacán, where she knows Fiske is headed, when Duke pops up in her back seat. Although annoyed, Joan allows Duke to accompany her, and they soon encounter Fiske in a roadside gas station. There Duke fights Fiske for his suitcase, but after the conman drives off, Duke discovers that the bag is filled with newspapers. Still determined, Duke and Joan continue toward Tehuacán together and reveal to each other how Fiske had robbed them. Duke explains that, while he was performing his duties as an army finance officer, Fiske stole a government payroll from him, and Duke is now suspected of being in league with Fiske. At that moment, Blake drives up behind Joan's car and starts firing at it. After a long chase, Duke and Joan finally stop Blake by forcing a herd of sheep onto the road. In Tehuacán, Duke and Joan track Fiske to a hotel and are surprised to find him drinking with Ortega. To confuse Ortega, Joan, Fiske and Duke all declare they are staying at the hotel, and Joan and Blake take advantage of the policeman's presence by trapping Fiske in his room. While Joan holds Fiske at gunpoint, Duke goes to search Fiske's car for the money. Fiske soon overpowers Joan, however, and takes off once again. When Duke returns to the room empty-handed, he sees Blake pulling up to the hotel. By pretending to be Duke's unwilling accomplice, Joan is able to divert Blake long enough to escape the hotel with Duke. Fiske, meanwhile, has moved a construction detour sign at a highway crossroad, causing Joan and Duke to take the wrong road. When the couple finally reaches the construction site, the foreman refuses to allow them to pass until Joan tells him that she and Duke are eloping and are being pursued by her domineering father. The foreman then stops Blake, allowing Joan and Duke enough time to catch up to Fiske, who has just arrived at a remote, guarded hacienda. As Duke and Joan approach the hacienda, they are fired on by the guards and take cover among some rocks. Although he manages to kill one guard, the inadequately armed Duke is taken prisoner with Joan. At the hacienda, Duke and Joan discover Fiske with Julius Seton, a fence who has paid the conman $150,000 in "clean" money in exchange for the $300,000 in "dirty" payroll money. After Seton orders that Fiske kill both Duke and Joan, Blake walks in and reveals that he is part of the conspiracy. The greedy Blake then shoots Fiske in the back and announces that he is going to kill Duke. After Blake telephones Ortega, telling him that he is bringing in Duke's dead body, Duke suggests that he also kill Seton, return the stolen money to the army and keep all of the "clean" money for himself. Suddenly concerned for his life, Seton pulls a gun on Blake, and in the ensuing confusion, a fight breaks out, in which Joan inadvertently shoots and wounds Seton, and Duke overwhelms Blake. His name cleared at last, Duke returns to Veracruz with Joan, where they kiss and warmly contemplate their future.