27	"The Alternative Factor"	March 30, 1967	


While orbiting an apparently dead planet, the Enterprise seems to experience a strange moment of "nonexistence." Captain Kirk discovers a man named Lazarus on the planet below, who claims the effect was caused by his "enemy," later revealed to be an insane version of Lazarus from an alternate dimension. The sane version of Lazarus asks for Kirk's help in defeating his counterpart.