 After the mysterious disappearance of an oil well owner, one of his workers, Gerardo ( Jorge Negrete  (qv)) assumes the business management. Soon, the owner s sister ( Libertad Lamarque  (qv)) arrives from Argentina, and, believing that Gerardo killed her brother to keep the wells for himself, she starts working as a singer under a false name in the same casino her brother disappeared, in order to find out what exactly happened.