The Eye of the Beholder
The disappearance of a scientific team lures the U.S.S. Enterprise to investigate near Lactra VII. The Starship Ariel is located there, abandoned, with the Captain having transported to the planet's surface. The U.S.S. Enterprise crew beams down to discover a series of unusual environments. On the planet the crew meets the Lactrans, a group of twenty foot slugs with intelligent capacities far beyond their own.