I Apenati (1982)

A withdrawn young man, living with his widowed mother in the center of Athens, spends his evenings gazing through his telescope at the stars. Soon, his obsession turns to voyeuristically spying on his neighbors in the apartments across the way. He grows enamored of one woman in particular--an unhappily married one, whom he soon discovers has been watcing him. Their relationship grows as a series nightly phone calls, but when she makes the bold step of coming to see him in person, the delicate balance of their connection is upset.