A Leap in the Dark (1980)

Judge Mauro Ponticelli (Michel Piccoli) has been raised by his older sister Marta (Anouk Aimée). However, Marta has been having mental problems and fantasizing about committing suicide, which concerns him greatly. She seems to recover when he introduces her to Giovanni Sciabola (Michele Placido), a brilliant actor, but Mauro then finds himself becoming jealous of their relationship.