Post-Invaders
In another short-lived series, Thinnes had the lead role on The Psychiatrist as Dr. James Whitman.
"Manhunter" (in which Thinnes tracks a bank robbery suspect) is a TV Film that was broadcast on British TV in 1972 (with The Man Hunter as its title) but was not shown on American TV until 1976. A similar title ("The Manhunter"), but with a different plot, was used for a 1974-filmed TV movie. He played an intrepid writer and investigator of the supernatural David Norliss in 1973's The Norliss Tapes, a pilot for an unproduced TV series, and portrayed a suspicious schoolmaster in the TV movie Satan's School for Girls.
He appeared in the disaster films Airport 1975 as the co-pilot, and The Hindenburg as a sadistic SS captain. Thinnes was cast in Alfred Hitchcock's 1976 film Family Plot in the role of nefarious jeweler Arthur Adamson when Hitchcock's first choice, William Devane, was unavailable. Thinnes had already shot several scenes for the film when Devane suddenly became available. Hitchcock fired Thinnes and re-shot all of his scenes. He confronted Hitchcock in a restaurant and asked the director why he was fired. Flabbergasted, Hitchcock simply looked at Thinnes until the actor left. Some shots of Thinnes as the character (from behind) remain in the film.
Thinnes appeared in the 1979 miniseries From Here to Eternity as Captain Dana Holmes.
During the 1982–1983 season, Thinnes appeared as Nick Hogan in 35 episodes of Falcon Crest. He later played Roger Collins in the 1991 revival of TV's Dark Shadows. He appeared on One Life to Live as Alex Crown from 1984 to 1985, and as Sloan Carpenter from 1992 to 1995. He also played a lead role in "The Final Chapter," the first episode of the 1977 series Quinn Martin's Tales of the Unexpected (known in the United Kingdom as Twist in the Tale), and in "The Crystal Scarab", a first-season episode of Poltergeist: The Legacy in 1996. Thinnes was once considered by Paramount for the part of Jean-Luc Picard in Star Trek: The Next Generation.
He appeared in the 1988 pilot episode of Law & Order, "Everybody's Favorite Bagman", as district attorney Alfred Wentworth. By the time the show was picked up in 1990, however, Thinnes was contractually obligated to another TV series (NBC's remake of Dark Shadows), and so his character was replaced with district attorney Adam Schiff, played by Steven Hill. Thinnes made two appearances in The X-Files as Jeremiah Smith, an alien rebel with healing and shape-shifting abilities.
Twice Thinnes appeared on the ABC soap opera One Life to Live playing two different characters. From 1984 to 1985, he played the role of "Alex Crown" and from 1992 to 1995, he played the role of "Gen. Sloan Carpenter". During both of his stints on the show, his characters became a father-in-law to the same character, Cassie Callison.
In 2005, Thinnes co-starred as Dr. Theophile Peyron in the movie The Eyes of Van Gogh about Vincent van Gogh (played by Alexander Barnett, who also wrote and directed) and his voluntary stay in an insane asylum. The movie focuses on Van Gogh's relationships with Dr. Peyron, as well as fellow expressionist Paul Gauguin, and his brother, Theo.