Kirk investigates an experimental facility for holding prisoners and finds a sinister scheme.

Kirk and a landing party are stranded on a planet due to a disease that causes any adult to die a painful death, and must deal with the local children who have survived.

The Enterprise picks up a intergalactic conman, Harry Mudd, and three incredibly beautiful women who harbor a dark secret.

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.

A strange alien substance causes the crew to lose their inhibitions.

While exploring the edge of the galaxy, the Enterprise encounters an energy barrier that gives some crewmen strange powers.

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…

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.

A skeleton Enterprise crew are assigned to test a revolutionary computer system that is given total control of the ship.

Kirk, Spock and McCoy are trapped in two parts of another planet’s past – a world threatened with destruction when its sun goes supernova.