With McCoy behaving strangely, Kirk thieves the Enterprise and heads back to the Genesis planet created in the previous movie and the site of Spock's final resting place.
Meanwhile, pack of predatory Klingons is investigating the Genesis probe for weapons potential.
Meanwhile a science team discover a young Vulcan on the Genesis planet.

Entertaining Star Trek romp despite being saddled with a plot that is a foregone conclusion thanks to the playing of the familiar cast and good work from newbies Chris Lloyd and Robin Curtis.

The London Underground ran an advert at the time, the text of which ran:
By the time it takes you to find a parking spot - they'll have found him.