The Third Word (Spanish: "La tercera palabra") is a 1956 Mexican film based on the Argentinian play of the same name written by Alejandro Casona.
Two aunts hire Margarita (Marga López) to educate their wild nephew Pablo (Pedro Infante) who has lived his life on a rural mountain ranch and knows little of civilization.
As his family gathers to ready Pablo to prove his sanity and ability to handle his inheritance, Margarita recognizes a previous lover in the lawyer present.
When Pablo finds out, his distress at what he believes is a betrayal not unlike his mother allows his relatives to urge the psychologist to deem him unfit to inherit.
His aunts approach Pablo and help him to understand that of the forces he knew (God and death), there is a third one, love, or "the third word", and he races after Margarita to bring her back.