The disappearance of a scientific team lures the U.S.S. Enterprise to
investigate near Lactra VII. The Starship Ariel is located there, abandoned in orbit.
Captain Kirk, Mister Spock, and Doctor McCoy beam down to the surface in search of the Ariel's crew and discover a series of unusual
environments. The landing party is then taken captive by the Lactrans, a group of twenty
foot slug-like creatures with intelligent capacities far beyond humans, and put on display as specimens in a zoo.
This episode was written by David P. Harmon, author of the original series episodes "The Deadly Years" and "A Piece of the Action".