"The Zero Hour" (also known as "Hollywood Radio Theater") was an American radio drama anthology series that aired from 1973 to 1974. It is notable for being hosted by the legendary Rod Serling, best known for "The Twilight Zone."Here are some key details about the series:

• Host: Rod Serling
• Genre: Mystery, adventure, and suspense anthology.
• Broadcast Period: September 3, 1973, to July 26, 1974 (two seasons). It debuted in syndication and was later picked up by the Mutual Broadcasting System.
• Format:Initially, stories were presented as five-part dramas, with a new chapter broadcast Monday through Friday, concluding the story on Friday. Each part was approximately 30 minutes long, including commercials.
• In April 1974, the format changed to single, self-contained 30-minute installments, though the same actor would often star in all five programs during a given week.
• Production: Don Hills produced the series for StudioHouse. The opening theme music was by Ferrante & Teicher.
• Content: The series adapted best-selling mystery novels and featured a cast of well-known actors from both radio's Golden Age and popular television personalities, including John Astin, Patty Duke Astin, Howard Duff, George Kennedy, Richard Crenna, and William Shatner. Some of the scripts were also written by Rod Serling himself.
• Episodes: There were a total of 130 episodes, counting each five-part show as five episodes.
• Legacy: Despite its relatively short run, "The Zero Hour" is credited with helping to spark a mini-resurgence of radio drama in the 1970s, paving the way for shows like the "CBS Radio Mystery Theater." It faced challenges with its initial serial format and a lack of promotion, which contributed to its cancellation.