The Lilith Necklace (1970)

A jilted lover comes to a detective, Louie, looking for his ex-girlfriend. Louie finds the girl, but in company of a notorious playboy who may have ulterior motives. As she digs into the past, Louie discovers an antique necklace at the center of everyone's declarations of love. The mystery unravels with a conclusion which may be to nobody's satisfaction . . .