Star Trek: A Guide to All the Mirror Universe Episodes

Warning: This article contains Star Trek: Discovery spoilers.

In this week’s episode of Star Trek: Discovery, we got confirmation that the crew of the Discovery has landed in the franchise’s Mirror Universe where, instead of the peace-loving Federation, Earth has its own, tyrannical Terran Empire.

The Star Trek franchise has a history of episodes and arcs that take place in this Mirror Universe. They are often amongst the strongest storytelling of their respective series and build upon the Mirror Universe mythology that has come before.

As we head further into Discovery‘s incarnation of the Mirror Universe, let’s look back at all of the Mirror Universe episodes in Star Trek‘s history…

The Original Series’ Mirror Universe

The one that started it all! The Original Series first ventured into the Mirror Universe in Season 2’s “Mirror, Mirror,” when four members of the Enterprise’s crew are switched with their nefarious counterparts in the Mirror Universe.

Discovery has drawn many of its Mirror Universe elements from this original incarnation, including the Agony Booths and the Terran Empire’s preferred method of job promotion: betrayal and murder.

Discovery also borrows “Mirror, Mirror”‘s logic that one does not simply travel to the Mirror Universe, but must switch places. The Mirror Universe’s Discovery has seemingly ended up in our Discovery’s universe, which will no doubt cause all manner of problems for the Federation.

There better be at least one goatee in Discovery‘s mirror universe or I’m asking for a refund. (Though Tilly’s Terran ‘do is a good start.)

Deep Space Nine’s Mirror Universe

Deep Space Nine did a deep dive into the Mirror Universe with five separate episodes across five different seasons: “Crossover” (Season 2), “Through the Looking Glass” (Season 3), “Shattered Mirror” (Season 4), “Resurrection” (Season 6), and “The Emperor’s New Cloak” (Season 7).

While the Deep Space Nine Mirror Universe story arc doesn’t seem to have much to do with Discovery‘s take so far, its thematic foundation of the narrative rested on the idea that those who visited the Mirror Universe had a positive effect on the Terran Empire, which began to reform itself for the better. Could the Discovery’s visit to the Mirror Universe have been part of that path to change?

DS9‘s visit to the Mirror Universe also introduced the idea that people who died in the “normal” universe might be alive and well in the Mirror Universe, as we found with Sisko’s wife. In “Despite Yourself,” we met Mirror Connor, another version of the Shenzhou’s ensign. It seems inevitable that we will meet more mirror versions of characters who’ve died in our universe. My favorite theory? That Phillipa Georgiou is the Emperor of the Terran Empire.

Enterprise’s Mirror Universe

Enterprise really hit its narrative stride when it ventured into the Mirror Universe in “In a Mirror, Darkly, Parts 1 & 2,” which saw the show imagining a fate for the USS Defiant, the missing ship the Enterprise is looking for in The Original Series episode “The Tholian Web.” 

What happened to the Defiant, per Enterprise canon? Basically, the crew went crazy, turned on each other, and ended up in the hands of the Tholians. The crew of the ISS Enterprise, captained by a Mirror Universe version of Jonathan Archer, steal the ship from the aliens and attempts to use it to overthrow the Empire. The Defiant has already had a mention in Discovery as a ship that has previously crossed over to the Mirror Universe.

These episodes give us the backstory for the Terran Empire, and how it ended up so different from our universe’s Federation. It imagines the famous first contact between human Zefram Cochrane and the Vulcans going very differently. Instead of a peaceful interaction, Cochrane kills the lead Vulcan and he and other humans loot the ship. Yeah, the Mirror Universe is the worst.