Ghalandar feels bothered by the suitors wooing for his sister Eshrat. But for a secret reason he does not want to marry her off. As a way out, he asks his trusted friend Sadegh to marry his sister, but warns him about making love with her. Sadegh tries to keep his promise, but when he leaves his wife immediately after the wedding ceremony for the capital, Eshrat follows and joins him and his mother. Unable to bear with the taunts of mother, Sadegh eventually breaks his oath and takes his legal wife to bed. Informed of this betrayal, Ghalandar waylays Sadegh at a dark night and stabs him to death. Eshrat, suspecting who is behind this murder, flees and joins a whorehouse, intent to exact her revenge by staining the name of his so-far respectable brother...