Kirk, freshly returned from prison, is with Spock, McCoy, Chekov, and Scott when the two dead assassins are discovered. Kirk suddenly steps away to talk more or less privately with Spock. Chekov looks around to see where they went...

...and this is what Chekov saw...

Then Spock looks Kirk deeply in the eyes and says, "It's possible." Well, it sure LOOKS possible! You know, Kirk and Spock could have been talking about ANYTHING right then. Consider the possibilities!