Hustle(1975)

She's the call girl. He's the cop. They both take their jobs seriously.

The body of teenager Gloria Hollinger is found dead on a Los Angeles beach, and Lt. Phil Gaines is in charge of the investigation. Gaines learns that the girl, a stripper and prostitute, committed suicide, but he ignores the connection between her and a powerful mob lawyer, Leo Sellers. Hollinger's father, however, is not satisfied with Gaines's results, and attempts to investigate the case on his own.