Kirk and his crew are at deadly risk from an alien creature that feeds on the salt in a human body and can take on any form.

Charlie Evans, the sole survivor of a transport crash, is transferred to the Enterprise from a different ship. Why are they so eager to rid themselves of him, though? There's more to Charlie than meets the eye...

A transporter malfunction causes Captain Kirk to split into his "good" and "evil" selves, and a landing party will freeze to death if they don't merge the two back together.

The Enterprise encounters a vast alien ship that threatens the Enterprise with destruction.

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.

Spock commands a stranded away team when their shuttlecraft is stranded on a planet with hostile natives.

The Enterprise must protect a very important shipment of grain from both Klingons and some adorable creatures called tribbles.