The Slender Thread

The Slender Thread is a 1965 drama film directed by Sydney Pollack and starring Sidney Poitier, Anne Bancroft, Telly Savalas, Edward Asner, and Dabney Coleman. Interesting. The relationships are well-developed. from Wikipedia:

Poitier portrays Alan, a college student who is volunteering at Seattle's then-new Crisis Clinic, a crisis call center. Shortly after beginning his night shift, Alan receives a call from a woman named Inga (Bancroft) who says she has just taken a lethal dose of pills and wants to talk to someone before she dies. The story line follows the efforts of Alan, a psychiatrist (Telly Savalas) and a detective (Ed Asner) to locate Inga and her husband (Steven Hill). Various flashback scenes depict the events that led Inga to make the attempt on her life.

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The New York Times calls it a "dark tale". Slant Magazine has a review. Variety says, "As a showy vehicle for talents of Sidney Poitier adn Anne Bancroft, the production offers mounting tension".

DVD Talk calls it "excellent". Rotten Tomatoes has an audience rating of 76%.