Kirk pits the Enterprise against an invisible spaceship testing the Federation's defenses.

The Enterprise crew take shore leave on a peaceful, pastoral planet... where their dreams and fantasies come to life.

The Enterprise encounters a seemingly peaceful civilization run by a "benevolent" being named Landru... who intends for them to join his people.

The Enterprise arrives at a planet to establish diplomatic relations and finds itself in the middle of a "peaceful" war that threatens to destroy the ship.

Kirk investigates a series of grisly murders on a mining planet that are the work of a seemingly hostile alien creature.

Kirk and Spock must travel into the past in order to correct a change that will alter history.