Question: What was the name of the 1975 American thriller film directed by and starring Clint Eastwood, co-starring American actor Jack Cassidy?

Context paragraphs:
The Eiger Sanction (film): The Eiger Sanction is a 1975 American thriller film directed by and starring Clint Eastwood.  Based on the 1972 novel "The Eiger Sanction" by Trevanian, the film is about an art history professor, mountain climber and former assassin once employed by a secret United States government agency who is blackmailed into returning to his deadly profession and do one more "sanction", a euphemism for killing.  He agrees to join an international climbing team in Switzerland planning an ascent of the Eiger north face in order to complete a second sanction to avenge the murder of an old friend.  The film was produced by Robert Daley for Eastwood's Malpaso Company, with Richard D. Zanuck and David Brown as executive producers, and co-starred George Kennedy, Vonetta McGee and Jack Cassidy.

Blood Work (film): Blood Work is a 2002 American mystery thriller film produced, directed by, and starring Clint Eastwood.  The film co-stars Jeff Daniels, Wanda De Jesús, and Anjelica Huston.  It is based on the novel of the same name by Michael Connelly.

Play Misty for Me: Play Misty for Me is a 1971 American psychological thriller film, directed by and starring Clint Eastwood, in his directorial debut.  Jessica Walter and Donna Mills co-star.  The original music score was composed by Dee Barton.  In the film, Eastwood plays the role of a radio disc jockey being stalked by an obsessed female fan.

Dirty Harry (2007 video game): Dirty Harry is a canceled video game that was in development by The Collective, Inc. intended to be published by Warner Bros.  Interactive.  The game was to continue the story of the 1971 film of the same name starring Clint Eastwood as Harry Callahan, the protagonist.  Clint Eastwood was intended to reprise his role, lending his voice and likeness as well as consulting and creative input.  The game was to follow the same storyline of the film, with the San Francisco detective tracking down a serial killer named Scorpio.  Versions were planned for both the PlayStation 3 and Xbox 360, with a release in 2007.

The Eiger Sanction: The Eiger Sanction is a 1972 thriller novel by Trevanian, the pen name of Rodney William Whitaker.  The story is about a classical art professor and collector who doubles as a professional assassin, and who is coerced out of retirement to avenge the murder of an old friend.  The novel was made into a film directed by and starring Clint Eastwood in 1975.  Whitaker wrote a sequel entitled "The Loo Sanction".

Jack Cassidy: John Joseph Edward "Jack" Cassidy (March 5, 1927 – December 12, 1976) was an American actor, singer and director of stage, film, and television.

White Hunter Black Heart: White Hunter Black Heart is a 1990 American adventure drama film directed by and starring Clint Eastwood and based on the 1953 book of the same name by Peter Viertel.  Viertel also co-wrote the script with James Bridges and Burt Kennedy.  The film is a thinly disguised account of writer Peter Viertel's experiences while working on the classic 1951 film "The African Queen", which was shot on location in Africa at a time when location shoots outside of the United States for American films were very rare.  The main character, brash director John Wilson, played by Eastwood, is based on real-life director John Huston.  Jeff Fahey plays Pete Verrill, a character based on Viertel.  George Dzundza's character is based on "African Queen" producer Sam Spiegel.  Marisa Berenson's character Kay Gibson and Richard Vanstone's character Phil Duncan, are based on Katharine Hepburn and Humphrey Bogart, respectively.

In the Line of Fire: In the Line of Fire is a 1993 American action thriller film, directed by Wolfgang Petersen and starring Clint Eastwood, John Malkovich and Rene Russo.  Written by Jeff Maguire, the film is about a disillusioned and obsessed former CIA agent who attempts to assassinate the President of the United States and the Secret Service agent who tracks him.  Eastwood's character is the sole active-duty Secret Service agent remaining from the detail guarding John F. Kennedy in Dallas, Texas, at the time of his assassination in 1963.  The film also stars Dylan McDermott, Gary Cole, John Mahoney, and Fred Thompson.

High Plains Drifter: High Plains Drifter is a 1973 American Western film directed by and starring Clint Eastwood, written by Ernest Tidyman, and produced by Robert Daley for Malpaso Company and Universal Pictures.  Eastwood plays a mysterious, prepotent stranger, meting out justice in a corrupt frontier mining town.  The film was influenced by the work of Eastwood's two major collaborators, film directors Sergio Leone and Don Siegel.

James Fargo: James Fargo (born August 14, 1938) is an American film director.  He directed numerous films from 1976 to 1998.  After serving as assistant director on many films starring Clint Eastwood, he was then given the chance to direct the third Dirty Harry film, "The Enforcer", in 1976.  Later he also directed Eastwood in 1978's "Every Which Way but Loose".  It would be his final film working with Eastwood.  Fargo has also directed other films such as "Caravans", "A Game for Vultures", "Voyage of the Rock Aliens", as well as two Chuck Norris films.

Supporting paragraphs: The Eiger Sanction (film) Jack Cassidy
Answer: The Eiger Sanction