Mercenaries of the Rio Grande

Original title: Der Schatz der Azteken

Dr. Karl Sternau, the personal physician of the count Bismarck, who spent much of his youth in Mexico, is sent back to that country during the occupation by French troops in the service of the Austrian 'Emperor' Maximilian, to carry an encouraging letter from U.S. President Lincoln to the nationalist Mexican president Benito Juarez.