Frank da Vinci

Dr. Leonard "Bones" McCoy meets a former girlfriend when the Enterprise brings supplies to a remote archaeological survey group. Still attractive to McCoy, the woman's current appearance and her colleague hide a deadly secret, ultimately revealed as a tragedy of ecology.

Raised from infancy by noncorporeal beings, 17-year-old Charles Evans is ferried by an Enterprise crew unaware of his true nature. Once aboard, the teenager develops a crush on Yeoman Rand and proves dangerously unable to wield his enormous psionic powers with maturity until higher authorities intervene.

An alien virus picked up from the now-dead Psi 2000 outpost strips the crew of their inhibitions, causing chaos as each individual is overcome by hidden emotions -- even Spock. Meanwhile, the disabled crew have left the Enterprise unable to react to the planet break-up below that is pulling them down.

While exploring an uncharted area of space, the Enterprise is outmatched and taken in tow by a massive spherical spaceship. Doomed by the imposing being Balok and his huge ship, Kirk finally resorts to a bluff about a self-destruct system that will also destroy Balok's ship -- and the gamble pays off with surprising results.

Just as his ship is destroyed by an asteroid field, conman Harry Mudd and his "cargo" of three beautiful wives for lonely miners are rescued by the Enterprise and arrested. The rescue burns out the big starship's dilithium crystals, but Kirk's unhappy reliance on Mudd's clients for replacements is in jeopardy when the women's real secret is exposed.

Ordered to open relations with Eminiar VII, the Enterprise finds itself tagged in a mutual "computer war" with the planet's neighbor, Vendikar. The idea that citizens report voluntarily for disintegration according to the program of the "clean" war drives Kirk to dirty things up at the source, forcing a real peace.