Kirk loses his memory and joins the descendants of a tribe of Native Americans.
Kirk, Spock, and McCoy beam down into an idyllic location next to a lake on the planet Amerind, reminiscent of the American Pacific Coast. Kirk remarks on the "duplication" of the planet's evolution as compared to Earth, while McCoy notes the beauty of the flora.
They come upon an obelisk of an elongated pyramidal shape, covered with unknown alien symbols. Spock notes that the obelisk is "an alien metal of some kind, an alloy resistant to probe." Even the age is beyond the tricorder's ability to date. Spock examines the symbols but can offer no insight into their meaning. He speculates that to build such a monument would require a civilization equal to or beyond the Federation's ability. McCoy brands the planet "an enigma."
The trio only has thirty minutes to explore before leaving the planet. They return to the lake and look across at a village which houses an indigenous, Native American-like tribe that is "a mixture of Navajo, Mohican, and Delaware" characteristics. Kirk feels it is similar to discovering a mythic lost society.