Despite the earlier Romulan war, the Romulans have never been seen in person. The Enterprise, in pursuit of a Romulan aggressor, makes a discovery that causes suspicion about a senior crew member.

When McCoy sees the White Rabbit from Alice in Wonderland, the crew begins to realize that the planet they are visiting seems to have the dangerous power to turn any thought into reality.

Crash landing on a planet populated by hostile giants, the 7-man crew of the shuttlecraft Galileo find themselves unable to communicate with the enterprise or to escape the planet's atmosphere.

Encountering an uncharted planet in an empty region of space, Kirk and his crew are entertained by Trelane, a playful being who lacks the self-control to wield his great psionic powers with discipline.

In a freak accident the Enterprise is sent back to 20th century Earth, and must find their way back without changing history.

Captain Kirk's career is at stake when he is put on trial for the loss of a crewman during an ion storm.

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

The Enterprise picks up a crew of genetic supermen from the 20th century... and their leader, Khan, plans to create a new empire.

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.

The Enterprise crew try to rescue colonists from deadly radiation, but instead encounter strange alien spores that seem to offer paradise.

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

The Federation and the Klingon Empire teeter on the brink of war as Kirk investigates Organia, a humble planet, inhabited by pacifists, that is unwittingly caught in the middle.

Kirk and Spock encounter an alien named Lazarus who claims to be from an anti-matter universe.

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

Kirk and the Enterprise must combat parasitic aliens threatening the lives of millions.

First Officer Spock returns to his home world for a brutal Vulcan mating ritual.