Unsatisfied with this, Tom's colleague Peter Cable (Charles Cioffi) pays their mutual friend and detective John Klute (Donald Sutherland) to investigate.
The only lead is some obscene letters written to a New York call girl Bree Daniels (Jane Fonda) that seem out of character. She gave little to the Police so Klute travels to NY and begins to follow her and record her phone calls to get leverage on her.
This is an unusual and intense thriller from Alan J. Pakula that avoids many of the 70s detective/sex worker cliches.
It's essentially Fonda's film with Sutherland having very little dialogue and agency. He does lean on her to find things out but it's her world we see not his with him following in her wake.
Worth a look, it has aged very well 7/10.