 2151. Starfleet has constructed its first vessel that is capable of exploring the universe and the launch of Enterprise is imminent. Then two alien races land in a cornfield near Broken Bow, Oklahoma. A Klingon is being chased by two yellow-skinned creatures. The Klingon gets rid of the two, but not of a farmer, who shoots him with a plasma rifle. Back at Starfleet headquarters the Vulcans, who have been advising and restraining the human race since Dr. Zefram Cochrane invented the plasma engine almost 100 years ago, announce that they will take the Klingon, Klaang, back to his home world Kronos. They urge the humans to postpone the launch of Enterprise. But for the first time Starfleet will not listen to the Vulcans and the decision is made to let Enterprise bring back Klaang. Barely underway Enterprise  systems fail and the ship is entered by the yellow-skinned aliens.