Jonny Quest (or Jonathan T. Quest) is a ten- or eleven-year-old boy (his exact age is never stated in any of the show's episodes, though a 1964 ABC promotional trailer gives Jonny's age as eleven), the son of Dr. Benton Quest, "one of the three top scientists in the world," and apparently something of a Renaissance man; his scientific and technical know-how spans many fields. According to Jonny's file (read by government agent Corvin), his mother is dead (first episode, "Mystery of the Lizard Men").
Government fears that Jonny could "fall into the wrong hands" resulted in the assignment of a bodyguard, Roger "Race" Bannon, from Intelligence One. Bannon guards and tutors Jonny and Hadji. Hadji is Dr. Quest's adopted son, an eleven-year-old Indian boy (his age was stated in one of the show's episodes, "Pirates from Below") who is seldom seen without his bejewelled turban and Nehru jacket.
The Quests have a compound in the Florida Keys (on the island of Palm Key), but their adventures take them all over the world. Jonny's pet, a small white bulldog named Bandit, often provides comic relief although at least once ("Skull and Double Crossbones") he was instrumental in foiling the bad guys.
Dr. Quest travels the globe studying scientific mysteries, which get him into scrapes with foes that range from espionage robots and electrical monsters to Egyptian mummies and pterosaurs. Although most menaces were unique to the episode, one recurring nemesis is known as Dr. Zin, an Asian mastermind. Race Bannon's mysterious old flame, Jezebel Jade, also occasionally appears.
Tim Matheson performed the voice of Jonny. Mike Road was "Race" Bannon, Danny Bravo was Hadji, and Dr. Benton Quest was voiced by John Stephenson for five episodes, and by Don Messick for the remainder of the shows. Messick also provided Bandit's vocal effects, which were combined with an archived clip of an actual dog's barking. The voices of Dr. Zin and other assorted characters were done by Vic Perrin, who is best remembered as the "Control Voice" for the original The Outer Limits television series.
The memorable theme music for the 1960s series, a percussion-heavy big band "spy jazz" piece with no lyrics, was written by Hoyt Curtin. The character Hadji was noted as the first major non-white character to be presented as an equal, sympathetic participant in the stories in American television.