A huge unmanned alien probe is heading for Earth, sending out strange radio signals: the powerful signals boil the seawater, interfere with nearby starships and cause extensive damage. At this time, Vice Admiral James Kirk and his crew are returning from Vulcan in the Bird of Prey (renamed "Bounty") stolen from the Klingons after completing the mission to resurrect Colonel Spock, although they already know that they will face charges in a military court: they are accused of stealing the Federation starship Enterprise and are responsible for her destruction. At this juncture, Spock, who is still recovering, discovers that the alien probe is trying to establish contact with humpback whales on Earth; unfortunately, humpback whales were extinct three centuries ago due to overhunting. Kirk orders the "Bounty" to enter a gravity ejection state, using the sun's gravity to travel through time and space to the late 20th century. The starship arrived in San Francisco, California, USA in 1986, and the crew hid the starship on a lawn in Golden Gate Park. They then searched for whales that could communicate with the alien probe, containers that could carry the whales aboard the starship, and materials that could restore the Bird-of-Prey's power supply, which had been nearly depleted during the starship's journey through time. Kirk and Spock eventually enlisted the help of a whale expert, Dr. Gillian Taylor, who cared for two humpback whales at the Sausalito Whale Society. After much difficulty - including convincing Taylor that they were indeed from the future - the Enterprise crew successfully rescued the two humpback whales and brought them to the future in time to save Earth. The crew was then brought before a federal commission to answer numerous charges. Spock, who was not named as a defendant, sided with the rest of the crew. In the end, in light of their newfound bravery, all charges against the remaining defendants, except for those against Admiral Kirk, were dropped. Kirk was found guilty of disobeying orders as a superior officer and was symbolically demoted to colonel as a punishment; but as a recognition of his heroic behavior, he was appointed captain of the Federation starship Enterprise-A. Dr. Taylor, who came to the 23rd century with the crew of the Enterprise, decided to join the Starfleet and become a scientific officer. The branch plot as the framework of the plot shows Spock gradually recovering his memory, the human traditions he had previously acquired and accepted, and his recognition of his own emotions. At the beginning of the film, he did not understand the meaning of his mother's questioning of his "feelings"; but by the end, he was able to realize the importance of "feelings" to humans, and asked his father to tell his mother that he "felt good."