Shortly after beginning his solo duty on the 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 Mark (Steven Hill), who is on a local fishing vessel.

Throughout the movie, the call is traced by hand through several electro-mechanical telephone central office switches which leads to the hotel where Inga was staying (at the Hyatt House, since demolished) near the Seattle–Tacoma International Airport.

Early one evening, psychology student Alan Newell (Sidney Poitier) rushes from the university to his shift as a volunteer telephone attendant at Seattle's then-new Crisis Clinic.

As he drives past the Ballard Bridge, he doesn’t notice the car being driven erratically in the opposite lane by a woman (Anne Bancroft) with whose path his will cross later on.

On January 6, 1965, it was announced in Daily Variety that Paramount Pictures had secured the rights to produce "Voice in the Wind," a screenplay written by Stirling Silliphant.

The script was based on the Life magazine article "Decision to Die," published on May 29, 1964, which chronicled the real-life story of a woman in Seattle, Washington, who attempted suicide.

In January 1965, Elizabeth Ashley was initially cast as "Inga Dyson," but a third party later informed her that she had been replaced by Anne Bancroft without formal notice.

Allegedly, Ashley had turned down a lucrative opportunity worth $100,000 due to her commitment to the project, leading to a legal dispute with the studio.

Poitier's scenes were filmed on a sound stage, while Bancroft read her lines offstage or through a receiver in her dressing room wired with a live telephone connection.

[2] The Slender Thread was slated for a special engagement at the Stanley Warner Theater in Beverly Hills, California, on December 15, 1965, to qualify for Academy Award consideration.