Trama

To save Earth from an alien probe, Admiral James T. Kirk and his fugitive crew go back in time to San Francisco in 1986 to retrieve the only beings who can communicate with it: humpback whales.

The most acclaimed Star Trek adventure of all time with an important message. It is the 23rd century, and a mysterious alien probe is threatening Earth by evaporating the oceans and destroying the atmosphere. In their frantic attempt to save mankind, Admiral Kirk and his crew must time travel back to 1986 San Francisco where they find a world of punk, pizza and exact-change buses that are as alien to them as anything they have ever encountered in the far-off reaches of the galaxy. William Shatner and Leonard Nimoy return as Kirk and Spock, along with the entire Star Trek crew.—Robert Lynch <docrlynch@yahoo.com>

It is the 23rd century, and a space probe appears over Earth, emanating strange sounds towards the planet, and apparently waiting for something. As time goes on, the probe starts to cause major storms on Earth and threaten its destruction. Admiral James T. Kirk and crew are called upon once again to save mankind. They discover the strange sounds are actually the songs of the humpback whale - which has been hunted to extinction. They have only one choice - to attempt to time travel back into the 20th century, locate two whales, and bring them back to 23rd century Earth to respond to the probe.—Colin Tinto <cst@imdb.com>

In 2286, an enormous cylindrical probe moves through space, sending out an undecodable signal and disabling the power of ships it passes. As it assumes orbit around Earth, its signal disables the global power grid and generates planetary storms, creating catastrophic, sun-blocking cloud cover. Starfleet Command sends out a planetary distress call and warns all starships not to approach Earth. On the planet Vulcan, the former officers of the USS Enterprise are living in exile, after the events of the previous film. Attended by Captain Spock (Leonard Nimoy), still recovering from his resurrection, the crew - except for Saavik (Robin Curtis), who remains on Vulcan - take their captured Klingon Bird-of-Prey (renamed the HMS Bounty) and return to Earth to face trial for their actions.

Receiving Starfleet's warning, Spock determines that the probe's signal matches the song of extinct humpback whales, and that the probe will continue to wreak havoc until its call is answered by the whales. He also reminds the crew that humpback whales were heavily hunted by humans and have been extinct since the 21st century. The crew uses their ship to travel back in time via a slingshot maneuver around the Sun, planning to return with a whale to answer the alien signal. The other officers are Leonard McCoy (DeForest Kelley), the chief medical officer; Montgomery Scott (James Doohan), the Enterprise's chief engineer; Hikaru Sulu (George Takei) the Enterprise's helmsman; Pavel Chekov (Walter Koenig) the Enterprise's navigator; and Uhura (Nichelle Nichols), the ship's communications officer.

Arriving in 1986, the crew finds their ship's power drained by the time travel maneuver. Hiding their ship in San Francisco's Golden Gate Park using its cloaking device, the crew split up to accomplish several tasks: Admiral James T. Kirk (William Shatner) and Spock attempt to locate humpback whales, while Montgomery Scott, Leonard McCoy, and Hikaru Sulu construct a tank to hold the whales they need for a return to the 23rd century. Uhura and Pavel Chekov are tasked to find a nuclear reactor, whose energy leakage will by collected and enable their ship's power to be restored.

Kirk and Spock discover a pair of whales in the care of Dr. Gillian Taylor (Catherine Hicks) at the Cetacean Institute and learn they will soon be released into the wild. Spock does a mind meld with a whale and figures out that it is preggers. Gillian is suspicious of Kirk and Spock, but Kirk manages to charm her and take her out to dinner. Kirk tells her of his mission and asks for the tracking frequency for the whales, but she refuses to cooperate. Meanwhile, Scott, McCoy and Sulu trade the formula of transparent aluminum for the materials needed for the whale tank. Uhura and Chekov locate a nuclear-powered ship, the aircraft carrier USS Enterprise. They collect the power they need but are discovered on board. Uhura is beamed back but Chekov is captured and severely injured in an escape attempt.

Gillian learns the whales have been released early and goes to Kirk for assistance. Gillian, Kirk and McCoy rescue Chekov from a nearby hospital and return to the now-recharged Bird-of-Prey. After saving the whales from whalers and transporting them aboard the ship, the crew returns with Gillian to their own time. On approaching Earth, the ship loses power due to the alien probe and comes down into the waters of San Francisco Bay. Once released from near-drowning, the whales respond to the probe's signal, causing the object to reverse its effects on Earth and return to the depths of space.

Later, the Enterprise crew stand trial before the Federation Council. The Council becomes grateful of the crew's part in saving the planet and drops all charges, save one for disobeying a superior officer. Kirk is demoted from Admiral and back the rank of Captain where he is returned to the command of a starship for his heroics. Kirk and Gillian part ways, as she has been assigned to a science vessel by Starfleet, while Spock's father Sarek (Mark Lenard) finally accepts his son's earlier choice to enter Starfleet. The crew departs on their ship, the newly christened USS Enterprise (NCC-1701-A), and leaves on a shakedown mission.