Kirk's defeat of Khan and the creation of the Genesis planet are hollow victories when your best Vulcan friend is dead and the ever-reliable Doc McCoy is going insane. Fortunately, Spock's father is on hand to explain that Spock Jr.'s 'living essence' (here comes the science part...) is in fact inhabiting McCoy's consciousness, hence his strange behaviour. Sensing the potential to restore things to the way things used to be, Kirk jacks the Enterprise in order to flee Genesis, in the hope this change of scene will shake McSpock into the two separate entities it was always meant to be. Unfortunately the Klingons have cottoned on to this plan and reckon it's a good time to take the boys in spandex out. I'm talkin' Downtown... Superior Star Trek feature film.