Zenite is needed to help stop a botanical plague. The Enterprise arrives at the planet Ardana, which has prepared a shipment of Zenite for them. As soon as Captain Kirk and Spock beam down to the Zenite mines, a group of miners met them at the landing site. Unfortunately, they were led by Vanna, leader of the Disrupters. She shows an attempt to take the Star Fleet officers hostage. The High Advisor Plasus arrives quickly with a security force. They were able to drive the miners off. Plasus invites Kirk and Spock to return to Stratos, the floating city in the clouds.

Kirk and Spock learn that the Ardanan society practices a form of social stratification. For example, Troglytes, who perform all physical labor on the planet, are separated from the City-Ddwellers, who live in luxury in the cloud city of Stratos. The Disruptors are a group of miners rebelling against Stratos's control.

Vanna attempts to take Kirk hostage. During the struggle, Kirk overpowers her. She accuses Kirk and the Enterprise of intimidating the Troglytes. Once Spock and Strattos Security arrive, she is taken into custody and interrogated under the "rays," an intense and painful torture device. When Kirk and Spock protest this torture, they are ordered off Stratos.

Kirk and Spock return to the Enterprise, where they learn that the unprocessed Zenite emits an odorless, invisible gas that diminishes mental capacity and heightens emotions. However, Spock believes that Troglytes forced to serve as City-Dwellers aboard the floating city are not affected by the gas, enabling them to organize the rebellion.

Kirk contacts Plasus and offers to supply the mines with filters to protect the miners from the Zenite gas. However, Plasus turns down Kirk's proposal. Kirk beams down to Vanna's holding cell, informs her of the harmful effects of zenite gas, and makes the offer filters available. Vanna is also skeptical but appears to trust him, and they both escape and return to the Zenite mines, only to be captured again by the Disruptors.

Vanna puts Kirk and Plasus to work in the mine. Unfortunately, the effects of the Zenite gas become apparent as Kirk and Plasus become increasingly irritable. After a fight, Vanna finally believes Kirk's story of the harmful gas and signals the Enterprise for help.

The Zenite consignment is eventually prepared for transport. Plasus has allowed the distribution of the filters, and Vanna declares that her people's struggle for equality will continue.

Cheers,
Hophead Jon