Ardana is a member of the United federation of Planets, it is a Class-M planet, with a red sky. Remarkably, one of its major cities, Startos, floats in the clouds. The wealthy inhabitants of Stratos have been given the fanciful name of the Cloud Minders.

According to Captain James T Kirk of the USS Enterprise, Stratros is one of the most beautiful and tranquil cities in the Galaxy. The city is designed in elegant simplicity reminiscent   of the ancient Greco-Roman style of Old Earth, and its inhabitants dedicate their lives to the study of philosophy and the arts, Kirk`s First Officer, Mr Spock, adds that Stratos is one of the finest examples he has ever seen of "sustained antigravity elevation".

Visitors arriving by transporter appear on a stage of balcony that on one side overlooks a great river many miles below on Ardana`s surface, and on the other side one of Stratos` public squares. The Stratos-dwellers have developed their own version of the transporter; users appear and disappear in what seems to be a flickering red c loud.

The leader of Ardana is the High Advisor. During the Enterprise`s visit in 2369 on Stardate 5818.4,  the High Advisor is Plasus and he has a charming and beautiful daughter named Droxine.

All the inhabitants of Stratos seem privileged. They live in spacious quarters and dress in elegant clothing. Plasus has long, flowing white robes. Droxine wears a halter top and a long harem-like start. Flowing from a single point at the back of her neck is a long cape, and her entire outfit is made of a light shimmering blue material. Her long hair is piled on top of her head in an unusual coiffure, and she wears elaborate earrings.

Security personal are known as Sentinels. They wear thigh-length robes held closed by wide black belts that match their high black boots. They wear large beret-like hats - very high on the one side and nearly flat on the other - and carry phaser-like weapons.

But all the beauty and sophistication of Stratos has its price. Far below Stratos, on the rugged surface of Ardana, zenite is mined by the Troglytes. Unlike the inhabitants of Stratos, the Troglytes live in primitive conditions and are forced to work in the mines. They wear uniform red coveralls, with a slate blue handkerchief protecting the throat.

Although the Stratos-dwellers believe that the Troglytes are inferior intellectually and emotionally, further study indicates that both the Troglytes and the Stratos-dwellers are actually members of the same race, all of whom once lived on the planet`s surface.

What causes the seeming subordinate nature of the Troglytes is the presence of zenite gas in the mining tunnels. After several hours the gas causes even the most reasonable of individuals to act irrationally and violently.

Zenite only gives off the gas in its natural form; after refining, it is entirely safe to use. Its ability to stop biological plagues is particularly prized.

The Troglytes are normally restricted to the planet`s surface - any Troglytes on Stratos are carefully monitored. Apparently, infractions are dealt with in various ways. While waiting to discover their fate, Troglytes are kept in pleasant airy jail cells with horizontal bars across the door.

Serious offenders are bound to an instrument of torture known as the rostrum, and must suffer bright flashing lights known only as rays. These lights clearly cause great pain.

Though a band of Troglytes called Disrupters has been fighting for equality for many years, it is not until the visit of the Enterprise that change seems possible for the people of Ardana. Dr McCoy discovers that, once away from its influence, even a person who has suffered for many years under the influence of zenite gas will recover his or her normal thoughts and feelings. McCoy fashions a filter mask so that whoever works in the mines may do so safely.

Captain Kirk offers the help of the Federation Bureau of Industralisation to mediate between the Stratos-dwellers and the Troglytes, but the matter still seems to be in doubt when the Enterprise leaves.