Star Trek IV: The Voyage Home is a 1986 motion picture released by Paramount Studios. It is the fourth feature film based on the Star Trek science fiction television series. It completes the story begun in Star Trek II: The Wrath of Khan and continued in Star Trek III: The Search for Spock. Intent on returning home to Earth to face trial for their crimes, the former crew of the USS Enterprise travels to Earth's past in order to save their present from a probe attempting to communicate with long-dead humpback whales. After directing The Search for Spock, cast member Leonard Nimoy was asked to direct the next feature, and given greater freedom to the film's content. Nimoy and producer Harve Bennett conceived a story with an environmental message. After dissatisfaction with the first script produced by Steve Meerson and Peter Krikes, Paramount hired The Wrath of Khan writer and director Nicholas Meyer, who collaborated with Bennett to rewrite the script. Principal photography started on February 24, 1986, with many real locations used as stand-ins for locations around San Francisco. Effects house Industrial Light & Magic assisted in postproduction chores, including the creation of animatronic whales. Composer Leonard Rosenman wrote the film's score. The Voyage Home's humor and unconventional story was well received by critics, fans of the series and the general audience. It was financially successful, earning $133 million worldwide. The film earned four Academy Award nominations, for Best Cinematography, Best Effects, Best Music and Best Sound.
A large cylindrical probe moves through space towards Earth, sending out an indecipherable signal and disabling the power of any vessel or station that it passes. As it takes up orbit around Earth, it continues signaling, disrupting the global power system and causing extreme weather patterns to develop over the planet while evaporating the oceans. Starfleet Command, on the last of its power reserves, sends out a subspace signal warning of the danger. On the planet Vulcan, the former officers of the USS Enterprise are living in exile after the events of Star Trek III: The Search for Spock. Accompanied by the Vulcan Spock, still recovering from his resurrection, the crew takes their stolen Klingon starship and head to Earth to face trial for their theft and destruction of the Enterprise. As they enter the solar system, they hear Starfleet's warning and the alien signal; Spock determines that it matches the song of humpback whales, long since extinct on Earth, and that the object will continue to wreak havoc on the planet until its call can be answered. The crew use their ship to travel back in time by a slingshot maneuver around the Sun; the plan is to go to the past and return with whales to repopulate the species. The crew travels back in time to the year 1986, but their ship's power is drained in the process. Hiding their ship using its cloaking device in San Francisco, the crew splits up to accomplish their tasks: James T. Kirk and Spock attempt to locate humpback whales, Montgomery Scott, Leonard McCoy and Hikaru Sulu must create a holding tank for the return trip, and Uhura and Pavel Chekov search for a way to recharge the ship. Kirk and Spock discover a pair of humpback whales"George" and "Gracie"in the care of Dr. Gillian Taylor at the Sausalito Cetacean Institute and learn they will soon be released into the wild. Kirk attempts to learn the tracking codes for the whales from Taylor, but is turned down. Scott, McCoy, and Sulu procure the necessary materials for the holding tank by giving the formula for transparent aluminum to a local manufacturer; Uhura and Chekov beam aboard a nuclear-powered aircraft carrier and draw some of its power to recharge their ship, but are discovered. Though Uhura is beamed back, Chekov is severely injured in an escape attempt and captured. Kirk and his allies rescue him from a hospital and return to the ship. The ship is successfully recharged, but Taylor learns the whales have been moved early. Kirk reluctantly allows her on the ship to get the tracking codes. The crew locates George and Gracie before they are killed by whalers, and transport the creatures into the waiting tank. With the intended cargo, the crew returns to the future. On approaching Earth, the ship loses power and crashes into San Francisco Bay. Once released, the whales respond to the probe's signal, causing the object to restore Earth and return to the depths of space. In light of their heroic actions in saving Earth, all pending charges against the Enterprise crew are waived; only Kirk is punished for disobeying a superior officer, and is demoted from Admiral to the rank of Captain, a punishment that restores him to the position he has lamented he never should have left years before. Dr. Taylor, having been brought to the future, takes a position on a science vessel. The crew departs for their ship, the newly-christened USS Enterprise (NCC-1701-A), to depart on a new mission into space.