
Spock was missing (obvious fact from the title) during the Genesis project activation in the Wrath of Khan. A Klingon spacehsip obtained a knowledge about Genesis and decided that it would be nice to have it as a means to preserve the Klingon race. They headed to the Genesis, blowing up some United Federation of Planets' starfleet along the way, kidnapping Lt.Saavik, Kirk's son, and Spock, and finally confront Admiral Kirk and his Enterprise crew.
Just like the second film, this third film was more of an action oriented film and more or less in a similar enjoyment level with the second film albeit with a horribly bad title. But again, i wouldn't recommend it to a newly breed viewers who were more accustomed to a high-octane actions. So unless you're interested in Star Trek series or believed that films were more than just a hobby or a killing time, don't bother.
My rating: **1/2 / **** - Kinda dragging toward the end, but the middle part was a o.kay.

A mysterious probe appears out of nowhere. Its origins unknown, only that it was "more intelligent race". This probe ignores every "peace" and "hello" signal and apparently had some kind of a magnetic field that rendered every starfleet or computer equipments within its close proximity useless. When it reaches Earth, it sends a signal toward the ocean, and when it doesn't receive a return signal, it apparently threatens to evaporate the ocean, generating a cloud that blocked most if not all of the surface of the Earth from the Sun. And clearly, it was bad news.
On Planet Vulcan, our beloved starfleet crew led by Admiral James T. Kirk who was now a fugitive for violating at least nine United Federation of Planets rules, were heading back to Earth, and quickly learned about the probe and its threatening existence. Spock deduced that the probe was signaling for Humpback whales, long extinct. Although seemingly unbased, Kirk and his crew travels back through time and bring back a couple of Humpback whales to save the Earth.
Nowadays, when we're talking about time-travel, "the Butterfly Effect" was fully realized up to a point where it could be said that even the casual film-goers would know about "the Butterfly Effect" in one way or another. This film involves a time-travel and it ignores every rule of "the Butterfly Effect". Not only does they bent a strand of grass, they taught a scientist about a science that is way ahead of his time, regrows an elderly's kidney, but they also bring back not just two Humpback whales, but probably millions of plankton contained in the water tank, and also a human. How's that for "the Butterfly Effect"? They just did enough damage to renders a new whole of race when they back to their own time. But you know, it always fun when we see a man from the future, with 300 years of added knowledge met with a man who has no knowledge about what future would holds. However, the fact that one of the crew keep complaining about the futility of the time irked me. I mean, come on, you had 300 years of added knowledge, you KNOW you were traveling in time, you really had no right to complain that these people you meet were primitive. If i was to travel back 300 years in time, i wouldn't complain if they didn't have any internet. Other than that though, i've grown enough love of Star Trek to be able to in some limited degree actually looking forward to their next adventure.
My rating: ** / **** - All sci-fi aside, its tone was the lightest in the franchise so far.