A Federation mission to a warrior planet gets tangled in tribal succession and a pregnant widow.
Kirk, Spock and McCoy beam down to Capella IV to win mining rights from the Capellans, a proud warrior people, but a Klingon named Kras is seeking the same agreement. A coup leaves the tribal leader Akaar dead, and his pregnant widow, Eleen, is condemned along with her unborn child.
The landing party flees into the hills with Eleen while the Enterprise is lured away by a false distress call. McCoy delivers her baby, and Kras is killed after his schemes are exposed. The baby becomes the new leader of the Capellans and is named Leonard James Akaar, after McCoy and Kirk.