Breaking news—a giant alien space cloud has been spotted entering the borders of the United Federation of Planets, which is headquartered on everyone's favorite planet: Earth.
And this terrifying cloud formation is heading straight for the capital planet. It'll be there in a matter of days. Panic time.
The only ship close enough to stop it is the starship Enterprise…which is currently undergoing renovations. Admiral James T. Kirk, the ship's former captain, seizes control of the ship from Captain Willard Decker, arguing that his experience makes him a better fit for the position. He then assembles his crew, which includes Leonard "Bones" McCoy, the ship's cantankerous medical officer, and Ilia, a former flame of Decker.
Enterprise launches into warp speed but an engine malfunction causes it to get caught in a wormhole. Decker countermands one of Kirk's orders during this emergency and, though this ticks Kirk off, his decision saves everyone's lives. Once they return to real space, they're met by Spock, the ship's former science officer, who wants to join the mission.
Recently, Spock has been going through the "Kolinahr" ritual of the Vulcan people, which is meant to rid one of emotions in favor of "pure logic." He failed after receiving strange messages from the space cloud that distracted him from his studies. To compound this, Spock's experiencing an internal conflict because he is half-human, making him more emotional than your average Vulcan.
Finally, Enterprise reaches the cloud and heads inside. The ship is immediately assaulted by the entity and Ilia seemingly disintegrates. Whoops. To the crew's shock, however, Ilia reappears moments later as an android created by the cloud to learn about the Enterprise. She also reveals the cloud's name: V'Ger.
Decker attempts to rekindle Ilia's memory, but it's no use. All she'll say is that V'Ger wants to find its Creator. Eager to learn more, Spock goes deeper into V'Ger and examines its memory banks, learning that it comes from a planet of sentient machines. He's horrified by its sense of "pure logic."
By now, V'Ger has reached Earth. It sends out old-fashioned radio signals in an attempt to contact the Creator, and when it receives no response, it threatens to destroy the planet. In a desperate gambit, Kirk says that he knows why the Creator hasn't responded, but that he needs to tell it to V'Ger directly. Ilia agrees.
Kirk, Spock, Decker, Bones, and Ilia head to the center of the cloud and find V'Ger, who turns out to be a small, ancient-looking space probe. To Kirk's shock, he learns that it's nothing more than the Voyager VI space probe that was launched by NASA hundreds of years ago, though it had attained consciousness after encountering the sentient machines.
Kirk tries to use the old NASA data codes to end the assault, but V'Ger sabotages itself—it wants to encounter the Creator directly. Perhaps motivated by his love for Ilia, Decker enters the code into the probe, and he and Ilia are evaporated in a stream of energy. The rest of the guys rush back to the Enterprise and skedaddle before the cloud dissipates.
Back on the ship, the crew wonders what they just witnessed. Perhaps the birth of a new species. Perhaps the next evolution of mankind. Either way, everyone is excited to be reunited and back to their adventuring ways.