Kirk and a landing party beam down to examine tritantium deposits and are attacked by a gaseous creature that feeds on red blood cells. Kirk remembers the creature as one that he fought - and failed to destroy - earlier in his career and where his mistake killed half the crew. Now the creature is stalking the Enterprise and Kirk is determined to destroy it no matter what the cost.
Star Trek chronicles the 23rd century adventures of the U.S.S. Enterprise, one of twelve state-of-the-art starships representing Starfleet, the exploration branch of the United Federation of Planets, an alliance of alien races including Earth, Vulcan, Tellar, and Andor.
Captain James T. Kirk, the youngest starship captain in the Fleet, commands the Enterprise with a combination of brashness, authority, and imagination. The half-Vulcan/half-human Mr. Spock serves as his extremely logical and efficient First Officer and Science Officer. The ship's chief medical officer is Dr. Leonard McCoy, who has supreme medical authority on the ship and tends to the physical and mental needs of the Enterprise's crew of approximately 430.
Other ranking crew members include: Montgomery Scott, a man dedicated to his ship engines but not adverse to a bit of shore leave; Hikaru Sulu, helmsman and a man of many hobbies ranging from botany to fencing, Nyota Uhura, the extremely competent head of Communications, and Pavel Chekov, brash young navigator with a fierce pride in his native Russia.