Movie star Dennis Morgan ("Christmas in Connecticut") played private detective Dennis Chase. Chase worked out of his posh apartment at 21 Beacon Street. But the apartment was in a generic American city, not Boston. Chase was an upscale private detective who sometimes did work for the government or the police.
Sexy Joanna Barnes ("Trials of O'Brien", "The Parent Trap") was Lola, Chase's secretary and a member of his team. Joanna Barnes later became a best selling novelist. She was married for a time to talented actor/director Lawrence Dobkin.
Handsome Brian Kelly ("Straightaway", "Flipper") was Brian, a young law student. Kelly's father had been governor of Michigan. Kelly attended the University of Michigan law school for a year. Kelly served as a marine during the Korean war. He was later seriously injured in a motorcycle accident that ended his acting career. He later tried to become a producer doing early development work on "Blade Runner".
Balding, middle-aged James Maloney was Jim, a science expert with a particular facility for electronics.
Dennis Chase would develop an elaborate plan to achieve the objective. Then he and his three crack associates would execute the plan. At least one episode involved the team performing an elaborate hoax on a criminal.
Each of the 13 episodes was 30 minutes. The series was on NBC on Thursday nights at 9:30 eastern time from July 1959 through September 1959. The series was then rerun on ABC from December 1959 to March 1960 at 10:30 on Sunday nights.
"21 Beacon Street" was a Filmways production produced by Al Simon ("The Burns and Allen Show", "The Jack Benny Program", "Mr. Ed", "The Beverly Hillbillies", "Green Acres").
The penultimate episode was titled "Nothing is Impossible", a coincidence(?) considering the "Mission: Impossible" connection.
Talented Laurence Heath wrote the pilot episode of "21 Beacon Street" and was the story editor.
The creators of "21 Beacon Street" later sued the producers of "Mission: Impossible" for plagiarism. The suit was settled out of court. "Mission: Impossible" creator and executive producer Bruce Geller claimed never to have seen "21 Beacon Street". But Laurence Heath of "21 Beacon Street" wrote several strong first season episodes of "Mission: Impossible" and later became a writer/producer of the series.
"21 Beacon Street" had a good cast and was a pretty good show. I particularly liked Joanna Barnes and Brian Kelly. I tried to watch it each week, but I tended to fall asleep.