A lonely young man, Mario, meets a lonely young woman, Natalia. Mario (Marcello Mastroianni) is lonely for social reasons; he is a stranger and a newcomer to town. Natalia (Maria Schell) is lonely because she has always lived in isolation, even in the heart of the city. Her loneliness is intensified because she is in love with a man (Jean Marais) who may not ever return to her, but who continues to occupy her heart to the exclusion of any other possible relationship.