The lightest - and one of the better - Trek films.Star Trek IV picks up where Star Trek III left off. The gang is all set to head home in their loaner, a Klingon Bird Of Prey. They take off, and encounter a huge space probe that's emitting these strange sounds. The crew deciphers these sounds as the cries of a humpback whale, now extinct in the 23rd century. Through whatever Trek logic, they determine that the probe, when it finds now humpback whales on Earth, will destroy it. In order to save the Earth, the crew decides to travel back in time and pick up a couple of whales, and take them back to the future (a whole other movie, that is).
So immediately, you know this isn't your basic, run-of-the-mill sci-fi.
They land in San Francisco, 20th century, plopping down and cloaking in Golden Gate Park ("Everybody remember where we parked"), in search of both whales and a viable power source to get themselves home again. Kirk and a culture-shocked Spock hook up with a whale expert (Catherine Hicks) and discover that her whales (not HER whales, but the whales she's overseeing at a marine park) are due to be released to the wild soon. Jackpot. Meanwhile, McCoy and Mr. Scott are building tanks on the ship for whales, and Uhura and Chekov are searching for power ("Where are your Nukelear Wessles?").
I think what most liked about STIV was that it was such a contrast to the previous two films. Wrath Of Khan and Search For Spock were both extremely heavy movies, and this one is a complete turnaround. While there are villains (whalers, natch), there's no central villain. The humor certainly didn't hurt.
It's not every day that you'd expect a Vulcan to be swearing like a champ, but there Spock is, speaking in colorful metaphors.
There are a few notable action sequences, but they're not central to the story. The plot is, admittedly, light for a sci-fi franchise. But the Trek movies do always sort of have the core dealing with the characters, and this film is no exception.If you can get past a sort of shaky plot, then you'll enjoy it.