Guest stars:

Stephen Brooks          Ensign Garrovick, new security officer
Jerry Ayres             Rizzo, one of the red shirts who dies after attack

   Lt Leslie, another red shirt who dies
   Ensign Pardoni, a red shirt who doesnt die.
   Total red shirts and others who die = 5

the creature: appears to be a gaseous cloud which can change molecular structure at will, thus eluding detection. Has an affinity for human red blood cells. Uses gravitation waves for propulsion through space. Intelligent. Spawns by fission only on its home planet (like the salmon?)

Crew Appearances:

Landing parties: Kirk and 3 red shirts (all 3 red shirts dead)
   Kirk and 5 red shirts (one red shirt dead, one injured_
   Kirk and Ensign Garrovick (Kirk sure puts himself in a pickle all the time, doesnt he?)
Spock, McCoy, Scotty, Nurse Chapel, Uhura, Chekov
Various expendable red shirts (creature attacks 2, one dead, the other injured when it enters the enterprize through the inpulse engine vent.

Kirk becomes obsessed when he has the opportunity to battle a gaseous creature that feeds on human blood cells, and one which he faced as a young inexperienced lieutenant 11 years ago. Half the crew of the USS Farragut perished during that earlier battle, and Kirk has blamed himself ever since because he had hesitated in firing his phaser at the creature. He is suspected of sacrificing all, the ship, his career, their mission, destroying the career of young Ensign Garravick, for this obsession but proves that he was right all along and figures a way of destroying the creature before it spawns.

Tritanium- a substance 21 x harder than diamond, being collected by the Enterprise

Dichoronium- a rare element the creature is made of

cordrazine- medicine used as a stimulant (also a significant factor in The City on the Edge of Forever)

Theta 7- planet awaiting vaccine carried by the Enterprise to the USS Yorktown

Tycho star system/Tycho 4- home of the creature

USS Yorktown- star ship set to rendezvous with the Enterprise
USS Farragut- star ship of Kirk's first deep space assingment 11 years ago, Captained by Garravick, young ensign Garravick's father, Killed by the creature .

Quotes:
"Yes, a smell. Strange smell. like being smothered in honey."
__________________
"Don't misunderstand my next question, Mr. Spock, but....why aren't you dead?"

Humor: OBSESSION

Kirk does his best to stop a killer cloud, but the crew has doubts about his sanity because they think he might be confusing it with just any killer cloud. Spock gives the OK to destroy it when he realizes it is an intelligent being.