The Scrubble were a silicate species indigenous to Jengus IV, resembling large humanoids composed of silicate minerals. They lived in caves and possessed the means to create special stones that were capable of picking up and manifesting the thoughts of nearby individuals.
The Federation was unaware of the Scrubble's existence when they established Outpost 76 on Jengus IV in the 24th century. After first contact was made by the outpost scientists, the two sides concocted a scheme to sell sensitive Starfleet intelligence on the black market, so that the scientists could buy better equipment and the Scrubble more rocks. They combined Federation and Scrubble technology to create a secret underground data mining center that could collect and store the thoughts gathered by Scrubble stones.
In 2381, Outpost 76 sent a distress call claiming that the Scrubble had attacked them with psychic mines. After a tentative peace agreement was brokered by Captain Murakami of the USS Hood, the USS Cerritos and USS Carlsbad were tasked with relocating the outpost and disposing of the mines.
The lead outpost scientist, Doctor Holden, and the Scrubble emissary arrived on the Cerritos for the treaty signing. The Scrubble leader presented a "sacred Scrubble totem" to Captains Carol Freeman and Maier, which was in fact a spy device intended to read their thoughts. Their plan was exposed by the Cerritos and Carlsbad away teams, who had discovered the data mining center on the surface, and by Ensign D'Vana Tendi, who noticed anomalous readings coming from the "totem". Holden and the Scrubble leader were taken into custody. (LD: "Mining The Mind's Mines")