"In a Mirror, Darkly" is the eighteenth and nineteenth episodes of the fourth season of the American science fiction television series Star Trek: Enterprise, and originally aired on April 22 and 29, 2005. This installment was developed to be a sequel to The Original Series episode "The Tholian Web" and a prequel to "Mirror, Mirror". The decision to set an Enterprise episode in the mirror universe originated with a pitch to enable William Shatner to appear in the series. The teleplays for both parts of the episode were written by Mike Sussman, with Manny Coto contributing the story for the second part.

The Gorn are a fictional extraterrestrial humanoid reptilian species in the American science fiction franchise Star Trek. They first appeared in a 1967 episode of the original series, "Arena", in which Captain Kirk fights an unnamed Gorn on a rocky planet. The fight scene has become one of the best-remembered scenes of the original series, in part due to the slow and lumbering movement of the Gorn, which some viewers have considered unintentionally comical.