Noir-style suspense thriller; three unrelated criminal schemes are happening on board an express train; all three get uncovered/solved/thwarted before they reach their destination.
The tragic romance between a woman with a dubious past and a young thief who reforms his life for love.
Alfonso, Eduardo and Cristina get lost when visiting a forest. A strange monk finds them and takes them to an ancient convent. There, the three amigos suffer personality changes, specially Cristina who tries to seduce Alfonso in a strange coincidence to a story told by an old monk. After some efforts to escape, Alfonso is trapped inside a jail and more strange and macabre situations happen.
Colonel Carrasco's wife Marta leaves him taking his young son. The child, Juan, grows into an admirable and well-mannered young man. Having been promoted to a higher rank of power amidst the Mexican Revolution, the indulgent and corrupt Colonel accepts a bribe to free a revolutionary, Felipe Martinez, from his prison. Martinez has been sentenced to execution at the hands of a firing squad. Carrasco asks to have the revolutionary replaced by absolutely anyone. In a twist of fate, that anyone turns out to be his own long lost son Juan. Upon receiving this news, Marta races to the prison and explains the predicament to Carrasco. He subsequently desperately attempts to prevent the gunning down of his son by his very own government officials.
Santa is a beautiful and very humble young girl living in Chimalistac, a small and quiet spot south of the 1930's Mexico City. After Santa is cheated by arrogant soldier Marcelino, she's rejected by her family and friends and expelled of Chimalistac. Santa finds shelter in a whorehouse and becomes a cinic and bitter woman, mistreated by bullfighter "Jarameno" and silently loved by blind pianist Hipólito.