Mary is called the "Midnight Flower" because each evening at midnight she does a wild dance atop a gaming table in a local gambling den. A young Spaniard in love with Mary, who would rescue her, stages a holdup at the most profitable table and passes the money on to her. In attempting to escape, she is caught, arrested, and jailed. While she is in prison, she meets a young evangelist who runs a mission in the slums. They fall in love, and on her release Mary joins him in the missionary work. This sets the local tongues wagging and complicates the affair until it is revealed that Mary is the daughter of a wealthy family--lost to a kidnapper when she was an infant.
