Marianela is an orphan young girl living in a small village where she guides the blind young son of a rich country man. She is secretly in love with him, knowing that he loves her only because he can't see her ugly face. But one day a famous doctor appears and promises to operate him so he can see. His father is happy to know this way he will be able to marry his rich cousin. Nela gets desperate knowing his luck will turn into her disgrace when he finally sees her face.

Basada en la obra de Pérez Galdós. Marianela es una muchacha muy humilde, llena de bondad e inocencia que lo poco que cae en sus manos se lo entrega a Felipe, un buen amigo suyo, para que pueda ir a estudiar a Madrid. Se martiriza pensando que Pablo, el joven al que sirve de lazarillo, pueda dejar de quererla por su aspecto cuando recupere la vista.