Barnaby Jones, when the series starts, has retired from being a private detective and turned over the business to his son Hal. When Hal is killed while on a case, his friend and fellow PI Frank Cannon offers to investigate the crime but Barnaby insists on looking into it himself. He not only finds the killer but also finds what's been missing from his life since retirement, and returns to active duty as a private eye.
In season five, Mark Shera joined the cast as J.R., the son of Barnaby's murdered cousin. Unlike Barnaby, he was more interested in being a lawyer than a detective.
With guest tropes in alphabetical order:
- Accidental Murder: On a number of occasions, notably "Dark Homecoming." A country singer is tricked into she's accidentally killed Kathy Lou, the insecure girlfriend of her ex in her hometown, with both Kathy Lou and the singer's slimy manager in on it. Unfortunately, Kathy Lou is soon Killed Off for Real when the trope gets played straight by the manager at the wheel of his car...
- Action Girl: Yes, amazingly Barnaby Jones had one - Alex Parks in "The Deadly Conspiracy." She throws a guy out a high window over her shoulder. Ouch.
- Artistic Title: The opening titles were animated and based around a motif of rectangles suggesting pieces of a jigsaw puzzle being put together.
- Bowdlerise: In season one's "The Murdering Class," the murderer announces his intention to frame a teacher for his crime by dubbing him "the n——r in the woodpile." This no longer being 1973, that word gets bleeped out on the DVD set.
- The Con Within A Con: "Gathering Of Thieves."
- Clear My Name: J.R. gets framed for murder in "Nightmare In Hawaii."
- The Exotic Detective: Okay, "he's really old" isn't the most exotic angle ever, but it's still an angle.
- Hollywood Silencer: Oddly subverted in season 1's "See Some Evil, Do Some Evil" as the silenced pistol makes a muffled yet audible noise the way a real suppressor would sound.
- Not the Fall That Kills You: In "Sing A Song Of Murder," a singer falls off a diving board into an empty swimming pool and lands on his head, and his manager and her colleague decide to cover it up by burying his body and making it look like he was kidnapped for a $500,000 ransom. Zig-zagged somewhat as the guy was still alive, and it was the asphyxiation that killed him.
- Old Master: This trope is played with in that he rarely ever engaged in fist fights or action scenes due to Buddy Ebsen's age making filming such scenes difficult. He's also an incredibly intelligent man who handles his work competently, is more than capable of performing his own forensic lab tests and he carries a gun, which he will use if necessary; and should all else fail he's on good terms with much of the police department and has more than enough backup should it become necessary.
- Opening Narration: Well, it is a QM Production. Example:
- Ooh, Me Accent's Slipping: British actress Anne Collings as the sister of the Victim of the Week in "A Trial Run For Death," her American accent wavers so much it nearly becomes another trope.
- Poorly Disguised Pilot: "The Killin' Cousin" was designed to be the pilot for a series about father-and-son private eyes called Tarkington. Not only did it not sell, it turned out to be the Series Finale (as well as the last first-run episode of any QM series to air).
- Shared Universe: The pilot establishes one with Cannon. The two shows later had a two-part crossover called "The Deadly Conspiracy" (which began on Cannon and finished on Barnaby Jones).
- Ugly Guy, Hot Wife: OK, ugly's pushing it, but the (considerable) gulf in attractiveness between Dick Van Patten's character and Jo Ann Harris'note is even noticed in-universe in "The Odd Man Loses." a nervous accountant (Van Patten) and two of his fellow and younger and better-looking carpoolers to carry out a robbery. Sadly for the accountant, his hot wife is cheating on him with one of the other carpoolers involved, who's also married. Sadly for him, she's got a bad case of Chronic Backstabbing Disorder complicated with Evil Is Sexy, you can guess this doesn't work out for anyone involved.
- Vacation Episode: "Nightmare in Hawaii" in the final season (given this aired on CBS, home of Steve McGarrett and Magnum, P.I., this isn't surprising).
- You Look Familiar: To name just one of many, many examples, Sharon Acker turned up in "Perchance To Kill" and again in "The Deadly Conspiracy" (crossing over with Cannon in more ways than one, as she appeared on that show's "The Salinas Jackpot" as well).