Someone to Watch Over Me (movie, 1987)

While Mike Keegan is celebrating his recent promotion to detective, in a fancy nightclub socialite Claire Gregory witnesses the murder of the owner by powerful mobster, Joey Venza. Mike is assigned to protect her in the night shift in her Manhattan apartment. When Venza threatens Claire, Mike and Claire eventually become closer—and Mike finds himself divided between the love for his family and his heated passion for Claire and his fascination of her world.