With this I have seen all 10 of the released Star Trek movies (and eagerly waiting for movie # 11). Star Trek IV : The Voyage Home is the most light hearted of the movies so far and it’s also the one where they’ve spent most time on Earth.
OK, so this is the 3rd and final installment of the trilogy of movies starting with Star Trek II : The Wrath Of Khan & begins 3 months after the events of Star Trek III : The Search For Spock. An unknown alien vessel, cylindrical in shape is headed towards earth, sending out an indecipherable signal and disabling the power of any vessel or station that it passes.The oceans begin to evaporate, causing severe weather conditions on earth. Meanwhile, exiled on Vulcan, our beloved crew decide to return to earth in the captured Klingon bird of prey and face punishment for stealing & then destroying the Enterprise.
The crew learn about the alien vessel; Spock is able to determine 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 it can be answered. The crew devise a plan to slingshot around the Sun to time travel back to the late 20th century and return with a whale. They arrive in 1986 era San Francisco and split up for the following – to find a whale, find a device to hold the whale and and Uhura and Chekov to search for a nuclear power source to repair the dilithium crystals.
There’s some fun as Spock jumps in the water to communicate with the whales, George & Gracie, and stuns the aquarium scientist by revealing the fact that Gracie is pregnant. McCoy & Scotty arrange for a large plexiglass tank to be built, which Sulu hauls in through a helicopter. But the scientist, Dr. Taylor, learns about the crew from the future and agrees to help out but she insists on coming along in the spaceship. Chekov is injured & captured on a navy ship while trying to power the crystals using the nuclear device on it. Dr. Taylor helps Kirk & McCoy get him out of the hospital.
Finally the crew with Dr. Taylor along for the ride go back to the 23rd century and release the whales in the San Fran bay. The whales answer the alien vessel’s signal and as a result, the vessel returns back to deep space while all power is restored on Earth. The crew are hailed as heroes but stand trial for disobeying orders. Kirk is demoted to the rank of a captain and given a new ship to command – the newly-christened USS Enterprise-NCC-1701-A, and depart on another mission with his crew.