An ancient probe, Nomad, believes Kirk is its creator and sets out to sterilise imperfection.
The Enterprise confronts Nomad, a small probe that has been destroying planets as part of its mission to find perfection. Nomad mistakes Kirk for its creator, Jackson Roykirk, and decides all imperfect life must be removed. Uhura's mind is wiped by the probe, and she must relearn her skills.
The story is a classic of artificial intelligence gone wrong, and Kirk ends the threat by exposing its logical flaw. The concept of Nomad was later reworked as the plot of the first Star Trek film, Star Trek: The Motion Picture, making it famous among fans.