10 Biggest Star Trek Plot Holes
4. Why Did You Leave Him On Genesis?
Now, there is a few pieces to this one. First, the Katra twist was a late in the day addition to the Wrath of Khan story, at the behest of Nimoy, so that he may not necessarily leave the franchise forever. The ending of that movie sees his coffin safely impacted on the surface of the Genesis Planet. Flash forward to the Enterprise's return home, and McCoy is beginning to lose his mind, as it is being pushed to the side by Spock's.
All good so far.
Sarek calls to see Kirk at his home, berating the Admiral for, in his opinion, abandoning Spock. Through a mind-meld, Sarek discovers that Spock did not give his Katra to Kirk. But, together, they discover that he did give it to McCoy.
All good so far.
At what point, however, does that jump to resurrecting the dead? Sarek himself says that Spock's body was in death. On the Genesis Planet, David Marcus and Saavik discover that Spock's body is both alive and cycling through the various stages of aging - but this is not related back to Starfleet. In fact, the USS Grissom is destroyed.
It has to be assumed, therefore, that Kirk - between his meeting with Sarek and his meeting with Admiral Morrow - discovered that Spock's body had come back to life. It is not stated on-screen, and it's a fairly large gamble to throw away his entire career on, without any confirmation!
What are friends for....?