At the end of that episode, the mining company and the horta had come to an agreement in which the mining company would stop destroying horta eggs and the horta would assist the miners with exploration and tunneling. As I recall, some of the horta eggs had hatched, and the boss of the mine was impressed with how fast the little ones could dig.
The hortas will start to rebuild their civilization, which will eventually lead to Federation recognition of their ownership rights to the world. Prior to that, the Federation will take over the world as a protectorate, and lease the mining area to the mining company, for the benefit of the hortas.
The mining company will hire the hortas for exploration and tunneling. The mining lease and the salaries paid to the hortas will make the hortas quite rich.
A Vulcan with mind-meld skill, or possibly a team of them, will be stationed at the mine to serve as a liaison between the mining company and the horta and its offspring.
In the sequel, the hortas' explorations have disclosed a large vein of naturally-occurring dilithium, and the mining company is starting to shift operations to extract this valuable strategic mineral.
However, a Vulcan lets slip during a mind-meld meeting with a horta envoy that he or she has discovered that the mining company and/or Federation officials have been skimming the hortas' rent and pension fund payments.
When the hot-tempered hortas learn about the theft, they go berserk and start attacking humans and equipment. "Money return our now" appears burned into the mine floors and walls.
The Enterprise is the closest Federation asset, and is called in to restore the peace and protect the newly-discovered dilithium.
That's how I would pitch it.
