Star Trek III starts off with the weary Enterprise crew returning home after their near-death battle with Khan, and the actual death of Spock, whose body had been torpedoed to the Genesis world, which was a newly transformed planet, formerly without life.  While all involved are a bit worse for wear, the biggest effect on a crew member seems to be with Dr. McCoy (DeForest Kelley), who is exhibiting strange behavior that suggests he may be cracking from the experience, babbling something about returning to Spock's homeworld of Vulcan.  Spock's father, Sarek (Mark Lenard), is convinced that Spock's "essence" has somehow been transferred to another before his death through a mind-meld, which would explain McCoy's behavior.  With an unknown life form recently found on the Genesis planet, Kirk (William Shatner) wants to visit and find out if Spock's body is also reincarnated, but the instability of the area makes it off-limits to anyone but science officers.  Kirk and company must hijack their old ship, against orders, but soon finds that murderous Klingons have discovered news of the Genesis Project, and are willing to kill anyone in order to gain information on the process. Leonard Nimoy directs.