Hermosillo's first collaboration with the writer Gabriel García Márquez (who makes a cameo appearance), Mary My Dearest explores the light and dark sides of fateful romance in a uniquely Mexican syntax. The first of the film's two parts is the capricious reunion of a cat burglar and his former mistress, María. They become partners in a traveling magic show, and for a time the magic spills over into their lives. The second part begins with the separation of the lovers by pure chance, when María, having car trouble, seeks help in a mental institution. The lovers become victims of a destiny they are powerless to change. The magical/realistic interchange in the plot allows Hermosillo even more opportunity than usual to slip unnoticed between the most mundane details of everyday life into the fantastic.