This entry in the immensely popular Star Trek series blends space fantasy with an ecology theme. On their way home to stand trial for stealing the Enterprise, the crew learns that an unidentified alien probe is threatening to destroy the earth by blocking the sun with a cloud cover. This mysterious spacecraft, they discern, is trying to communicate with whales, but unfortunately these mammals are extinct on twenty-third-century earth. Spock figures out a solution: time travel back to twentieth-century earth and bring back some whales to sing for the probe.
Can their Klingon spaceship survive warp speed? Yes, even if it shakes, rattles, and rolls. They park the vehicle in San Francisco in Golden Gate Park in 1986 and fan out to find the whales already in grave danger on the open seas. Kirk (William Shatner) smooth talks Dr. Gillian Taylor (Catherine Hicks), a marine biologist, into cooperating with them, although she finds Spock (Leonard Nimoy) to be very odd. The other Star Trek folk are amazed by the primitive state of computer technology, medicine, the production of plastics, and security aboard nuclear-powered ships.
The Star Trek series of movies keeps getting better, and this one was the best yet with its save-the-whales theme, its funny back-to-the-future adventure, and its surprise ending.