Season synopsis
Contains spoilers for this season and earlier seasons.
The Enterprise continues its separate missions in a season that sends the crew into Romulan space, across strange societies and into the past. In “The Enterprise Incident,” Kirk appears irrational as he takes the ship across the Neutral Zone. Spock publicly challenges him, then appears to kill him with a Vulcan death grip. The staged crisis lets Kirk return disguised as a Romulan and steal a cloaking device. Spock stalls while Scotty installs it, and the Enterprise escapes with the Romulan commander aboard as a prisoner. The mission succeeds, though the commander’s trust in Spock and Kirk has been used against her.
In “All Our Yesterdays,” the crew visits Sarpeidon shortly before its sun is due to explode and finds the population gone. A librarian’s atavachron sends Kirk, Spock and McCoy into different periods of the planet’s past. Kirk is arrested in a witchcraft-obsessed era, while Spock and McCoy land in an ice age. Spock becomes emotionally attached to Zarabeth and begins behaving like an earlier Vulcan, but McCoy persuades him that they must return. Following Kirk’s voice, the three reunite in the library and beam back to the Enterprise just before the star’s destruction.
In the final aired story, “Turnabout Intruder,” Janice Lester, a former partner of Kirk’s, uses an alien device to exchange bodies with him and takes command of the Enterprise. Kirk tries to convince the crew that he is trapped in Lester’s body, while Lester directs the ship toward a colony where she intends to leave him behind. Spock and the others grow suspicious of her erratic decisions. Lester orders executions, turning the senior officers against her. When the exchange reverses, Kirk regains command and her accomplice Coleman offers to care for her.