While doing atmospheric research in Africa, Dr. Quest discovers an inaccessibly high plateau, populated by prehistoric cavemen, who have been trained as slave laborers (for diamond mining) by a Nazi war criminal in hiding named Klaus Heinrich von Dueffel.

Dr. Quest comes to the aid of a fellow scientist who has accidentally created an (invisible) energy monster on a South Pacific Island. Generally remembered as the most frightening episode in the series.

Jonny and Hadji are marooned (by shipwreck) on the jungle coast of Africa, where they are adopted by a tribe of friendly apes who protect them from a pair of Australian poachers, intent on kidnapping them for ransom.

The Quest family home in Florida is attacked by foreign (submarine-borne) agents, intent on stealing a new undersea crawling vehicle that Dr. Quest is developing for the United States Navy.

While hunting for petrified wood samples in the forests of Canada, Dr. Quest is threatened by a gang of lumberjacks (one of whom disguises himself as a werewolf) intent on protecting their gold smuggling operation.

While investigating unusual eruptions on a tropical island, Dr. Quest discovers a secret ray gun base (operated by his nemesis, Dr. Zin, and protected by hovercraft-mounted guards), hidden deep within a local volcano.

While searching for a rare strategic mineral in the Amazon Jungle, Dr. Quest discovers a Pterondon trained by a wheelchair-bound slave driver to capture native workers needed for his mining operation.

On a visit to Japan, Dr. Quest finds that an old biologist friend (having gone insane) is breeding over-sized carnivorous lizards for the purpose of hunting human prey.  

When members of his extended family go down in a plane crash over uncharted jungle, Dr. Quest must rescue them (with the help of Local authorities) from a tribe of hostile Pygmy warriors.

While researching marine biology in the Caribbean, Dr. Quest discovers a phony witch doctor, who is protecting a secret submarine base (under construction by a criminal contractor) with his supposed voodoo powers.

A new cook aboard the Quest research vessel betrays his employer to a band of Mexican pirates (seeking sunken treasure, discovered by Jonny) in the Caribbean Sea.

After an emergency landing in the Andes Mountains Quest family bodyguard Race Bannon is challenged to an aerial dogfight by Baron Heinrich von Frohleich, an old German fighter ace (who keeps a collection of vintage aircraft at his Bavarian-style castle