 PLOT: Garth changes into the likeness of Spock. A few moments later,  he knocks Marta unconscious with the Vulcan nerve pinch. Since only  Vulcans can perform the pinch, she would have had to pretend to be  knocked out. His disguise was impromptu so he couldnt have planned  this display with her, and she shouldnt have known immediately what  to do when he touched her neck.