After a near-collision with a black star, the Enterprise is thrown back to 20th century Earth. They rescue an Air Force pilot, John Christopher, when his ship breaks up in their tractor beam, but realize they have created a paradox: they can't send him back to Earth with knowledge of the future, but if they take him with them to the future then his son will never be born and history will be changed.
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.