At a Christmas party, María Méndez (Dolores del Río) learns that Magdalena, her twin sister, has a comfortable lifestyle. María kills her sister and assumes her identity and lifestyle. However, her life becomes complicated by her late sister's sleazy boyfriend Fernando (Víctor Junco), and by Roberto (Agustín Irusta), who loved Magdalena.
The 96-page script was originally titled "The Other Woman" by José Revueltas, Jack Wagner and Roberto Gavaldón from a story by Ryan James. The Paul Kohler Agency represented the screenwriters.