Plasus was also the father of Droxine.
As a Stratos City Dweller, Plasus believed the Troglytes, the miner class on the planet, to be an inferior race, and continued Ardana's long-standing policy of apartheid, denying them of the privileges enjoyed by the Stratos dwellers.
In 2269, Captain James T. Kirk of the USS Enterprise abducted Plasus from Stratos to a zenite mine on Ardana, to convince him of the deleterious effects of zenite gas. Plasus finally accepted this proof, but threatened to press charges against Kirk. (TOS episode & Star Trek 6 novelization: The Cloud Minders)
Though he initially backed down from this threat, Plasus did file charges with the Starfleet Command Appeals Board. The Board rejected Plasus's complaint, concluding Kirk acted appropriately on behalf of an oppressed people. Plasus cut off relations with the Federation, and had a new anti-transporter defensive shield installed in Stratos. Shortly after, the Stratos City Dwellers launched a war against the Troglytes, who had formed their own government. This war, call the Great Disruption, eventually ended with the overthrow of Plasus's government and abandonment of Stratos. The ultimate fate of Plasus himself is unknown. (CoE eBook: Signs from Heaven)