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.

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

Spock kidnaps his former captain, the crippled Christopher Pike, and heads for a quarantined planet, putting his career and Kirk's life on the line.

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

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