A mysterious cloud-like object is heading for Earth and destroying everything in its path. The only ship in range is the newly refurbished USS Enterprise, so Admiral Kirk returns to his old command and warps out to intercept the enemy.
Warp is a word we've come to associate with fast because we're so familiar with Star Trek terms and yet nothing in this first Trek film moves above a glacial speed.
The problem is that between the TV show's cancellation and this film's production, the fans had hyped-up the series to such an extend that its own creators believed it to be vastly more significant and important than it ever was.
So this isn't Trek, it's sub-"2001" with desperately serious people out to solve what they insist is a desperately serious problem - or even deep social issue - yet it feels just like a dozen other TV plots.
That said, the critical failure of this film meant the sequel and all subsequent Trek movies (perhaps bar "First Contact") ventured too far in the other direction and became variously entertaining comic strip.
And though each of those improved on the special effects, it's only in this movie that the Enterprise looks like a real ship.
For years, the best way to watch this film has been to first read actor Walter Koenig's hilarious book "Chekov's Enterprise" about the making of this. But a director's cut DVD of the movie is being made that promises to be shorter.