Blanca, a young woman living in Odesa, is forced to kill a communist commissar to defend her honor. To escape persecution, she marries Carlos, captain of the Spanish steamship Campuzano, and leaves Russia. While Carlos returns to Madrid with his girlfriend Mary Lis, Blanca heads to Paris to annul her marriage. Some time later, in 1936, Carlos manages to impose his authority on the Campuzano's crew and ensure that the ship remains loyal to Franco's rebels. On one of his voyages, he encounters Blanca and tells her that Mary Lis is being held prisoner in a Cheka prison in Madrid.