Star Trek - IV, The Voyage Home

Star Date: 1986
How on earth can they save the future?

Star Trek IV
The Voyage Home

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Earth is threatened by large object that transmits a signal disabling the global power system and causing extreme weather patterns to develop. Spock determines the alien signal matches the song of humpback whales, extinct on Earth since the mid-21st century (at least 200 years). The crew devises a plan to go back in time, before the extinction, and return with a whale.

Arriving in the late 20th century, Kirk and Spock are able to quickly discover a pair of humpback whales, "George" and "Gracie," at the Cetacean Institute, an aquarium devoted exclusively to whales, and are told by the Institute's whale expert, Dr. Gillian Taylor, that the whales are shortly going to be released into the wild, making the pair ideal for their needs. Despite some upsets and the threat of whalers, the crew is able to return to the future, splashing down into San Francisco Bay, where Kirk releases the whales from the cargo hold. The whales respond to the alien signal, causing the object to restore Earth to its normal condition and to return to the depths of outer space.