Jengus IV is a planet where the rock-like Scrubble and Federation scientists conduct peace talks over a field of psychic landmines.
Jengus IV is home to the Scrubble, rock-like aliens negotiating peace with Federation scientists on the planet. In Mining the Mind's Mines, the Cerritos and the USS Carlsbad are sent to finalize the agreement while Mariner, Boimler and Rutherford help deactivate the Scrubble's psychic landmines.
The mines tempt people with visions of their fantasies before turning them to stone, and when several break they show nightmares instead. Fleeing into a cave, the ensigns find a lab where the Scrubble and the scientists have been secretly working together to gather Starfleet data.