Klute (1971) - Alan J. Pakula
John Klute's friend has totally disappeared. The only clue a connection with a call girl, Bree Daniels. Klute taps her phone in order to gain evidence against her to blackmail her into helping him find his friend. While Klute searches, someone is stalking Bree. After a businessman disappears the FBI draw a blank except for some unpleasant letters he wrote to a call-girl. His small-town friend John Klute travels to the big city to seek her out. At first their relationship is wary, and she sees him as just another guy to manipulate. But someone may already be stalking her, and as Klute's activities add to the danger a bond of sorts starts to grow.