Meu palpite é que você está procurando o episódio Star Trek "O fator alternativo" , da série 1, episódio # 27.
Anti-Lazarus calmly admits to stealing the Enterprise's dilithium. He
informs Kirk that his people thought that two universes exist in which
attempts to prove it, caused their destruction. Anti-Lazarus tells
Kirk that only one Lazarus can exist in one universe simultaneously.
Lazarus's time traveling ship is the "dimensional door," and connects
both Anti-Lazarus and Lazarus; only by destroying the ship with the
two Lazarus inside "dimensional corridor" which links the universes
can both universes be saved.
Kirk confronts Lazarus, and pushes him into the "dimensional door."
Kirk heads back to the Enterprise, ordering the ship's phasers to
target the dimension ship. The two Lazaruses meet once more and fight
as phaser beams vaporize the ship, sealing the two for all of
eternity, caught together between universes.
É no "corredor dimensional" que ocorre a imagem reversa.
Eu vejo que @NKCampbell encontrou o mesmo episódio ... então 2 pessoas ao mesmo tempo:)