The Blood Stain (1943)

Camelia, a prostitute who works in a low-class cabaret in Mexico City (called "The Blood Stain') meets Guillermo, a young man from the country who just arrived in the city looking for a better life. She offers to take care of him until he gets set up, and the initial friendship soon turns romantic. This inevitably causes problems with Gastón, Camelia's pimp.