The animation film is based on an old Russian ballad of how an evil wizard-werewolf hated his son, seeing no inclination to evil in him, and sent him to his death. He orders his son to return only "when the sand sprouts" (which is what the film's title is). The two sisters of the unfortunate young man, using magic of sisterly love, follow him and protect him from the evil magician as long as they can and, later, avenge his death on their murdering father - IMDB