This 1970s classic gave Jane Fonda in the sort of role that appealed to the permissive appetites of the time, a Best Actress Oscar for her performance as Bree Daniels, a New York call-girl. For reasons that are not altogether clear however the film's title refers to the small town Pennsylvania private detective. Klute, who is hired to track down an engineer researcher, who also happens to be Klute's friend, who never returned from a business trip to New York City. Klute's investigations leads him to Bree and a prickly relationship forms between them.
Much more effective as drama than as a thriller (indeed this aspect is largely peripheral), screenwriters Andy and Dave Lewis make Fonda's character the main focus of interest using to good effect the convenient device of Bree's sessions with a lady psychiatrist to explore her inner world and feeding this into the development of her relationship with Klute rather than exploiting its sexually sensationalist potential (nevertheless feminists subsequently pounced on the film as demeaning to women). Sutherland's typically understated performance provides a solid foil for Fonda's more high-strung persona as Klute's sang-froid does for Bree's nerviness.
The other major aspect of interest is Pakula's telling use of New York's decayed condition at the time as a resonant setting for this journey into the dark reaches of the psyche whilst the Zeitgeist tendency to paranoia evidenced by the prominent use of tape recorders would turn up in a more developed form in Coppola's The Conversation (1974).
FYI: Fonda had already turned in a first class performance in another Zeitgeist classic Sydney Pollack's They Shoot Horses, Don't They ? (1969)