Doug is an American mining engineer. Pres. Valdez of Paragonia (Aitken) wants him to reopen the country's mines. Doug is not interested ... until he sees the President's beautiful daughter, Juana (Rubens). Valdez returns to Paragonia, but is deposed by Generals Sanchez and Garcia and locked in San Mateo Prison. The Americano arrives. His company's local office has been ransacked, but he finds loyal caretaker Dan (Wilson) in hiding there. He is contacted by former Prime Minister Castille, now in disguise as a peddler... Valdez writes the mysterious date "23 Noviembre 1899" on scraps of paper which are then thrown from the prison window as garbage. Juana checks her father's diary. That date contains an account of a successful escape from San Mateo, using the secret tunnel! But Garcia demands that Juana marry him the next day or Valdez will die...