In theaters on 1986. It was a hilarious and a serious movie at the same time. That is what made this film a hit.

Star Trek IV: The Voyage Home
Summary:
This movie begins after Star Trek III ends. The crew is stuck on Vulcan with a stinky bird of prey, they name, the Bounty. After the repairs were finished, they took off heading for home. En Route, they overhear a message from Earth stating that oceans are going crazy and the whole Earth was going haywire by this probe in orbit. Kirk and crew discover that the probes transmissions are "whale song". To be specific, humpback whales. In the 23rd Century, they are all extinct. So Spock comes up with this crazy plan to back in time, retrive these whales, and go foreward in time, drop them into San Fransisco bay, and hope they tell the probe to "get the hell out of here". Kirk agrees, McCoy insults Spock some more, and their off!
When they arrive ( in the middle of Goldengate Park) in 1986, they found it to be psyco land. They managa their way through many obstacles until they find these two whales (George and Gracie) in a San Fransisco aquarium. Kirk convinces the lady in charge of them (with much debate and skeptisism) to give them the whales. She ends up tagging along the journy back to the 23rd Century. When they arrive, they save humanity once again. Now, of course there was much more plot and involvement in this movie. But, this is just a run down on the main plot.   

Screenshots:

My Review:

Music: The music was very nice as usual with Trek films. 4.5/5
Enjoyability: More like humor. This movies was as hilarious as it gets. 5/5
Plot: Good plot, but whenever time travel comes up, things get dicey. 4/5
Overall: A great movie and one of the best Trek films made. I thouroghly enjoyed this and it's definately worth watching, if not over and over again. 4.5/5