Star Trek: Discovery Just Entered the Mirror Universe

WARNING: This article contains spoilers for this week's episode of Star Trek: Discovery, "Choose Your Pain," which premiered Sunday.

Contrary to its title, "Choose Your Pain," this week's episode of Star Trek: Discovery seemed poised to end happily for everyone involved -- well, everyone not named Harry Mudd: Captain Lorca escaped from the Klingons, the tardigrade was set free, and Lt. Stamets and Dr. Culber, previously positioned as workplace rivals, were revealed to be a couple. But their shared moment of domesticity in the episode's final moments -- brushing their teeth together before heading off to bed -- was punctuated by a moment lifted straight from a horror film as Stamets' smiling reflection lingered after he'd walked away.

What should we make of that?

The most likely explanation -- oh, heck, perhaps the only explanation -- is that the reflection is the Stamets from the mirror universe, a parallel universe introduced in the beloved Star Trek: The Original Series Season 2 episode "Mirror, Mirror." In it, a transporter malfunction (surprise!) causes Kirk, McCoy, Scotty and Uhura to materialize on the Imperial Starship Enterprise, a darker version of the vessel they know, where officers assassinate their superiors in order to gain higher ranks, torture is used as a form of discipline, and (most sinister of all) Spock has facial hair. Their barbaric counterparts appear in their place aboard the USS Enterprise but, so we're told, that universe's Spock immediately recognized they were doppelgangers, and threw them in the brig.

Kirk & Co. avoided assassination and returned to their universe, with help from bearded Spock, and returned safe and sound to Enterprise, but the franchise was far from finished with the mirror universe, which was revisited in five episodes of Deep Space Nine and in two episodes of Enterprise, a TOS prequel.

Within the mirror universe, the United Federation of Planets is replaced by the brutal Terran Empire, which began when first contact with Vulcan was interpreted an alien invasion. The first Vulcan to step foot on Earth was shot (by Zefram Cochrane, no less), as recounted in the Enterprise episode "In a Mirror, Darkly," and the ship raided for its advanced technology, allowing the Terrans to expand well beyond the planet, conquering the races they encountered.

We've known for about a month that Discovery would return to the mirror universe, although given the drama's serialized nature -- far more so than any previous Star Trek -- it was difficult to imagine how. With "Choose Your Pain," we got our first indications.

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Without diving too deep into the blend of real-world scientific theory and nonsensical techno-babble that forms the "secret" of USS Discovery, the vessel is outfitted with an experimental displacement-activated spore hub drive that, as the name suggests, uses spores to jump across the Mycelial network, a microscopic web that stretches across the cosmos. It allows the ship to appear, virtually instantaneously, at any plotted location in the galaxy, and then disappear just as quickly. However, as the fate of its sister ship, the USS Glenn, shows, the system has its problems; until recently, Discovery could only jump relatively short distances, because of navigational instability, an issue the Glenn was able to overcome with the help of a mysterious "super computer."

Enter the tardigrade, an enormous, outer-space counterpart to the resilient micro-animal found on Earth. Nicknamed "Ripper" by the Discovery away team that found it on the Glenn, and misinterpreted its behavior, the tardigrade was quickly deduced by Michael Burnham to be the missing piece of the spore-drive puzzle: Through symbiosis, Ripper communicates with the spores, and when tied in to the engineering system, instinctively performs the calculations required for long jumps. But just when it seemed Discovery's problems had been solved, and Starfleet could begin outfitting additional ships with spore drives (all the while searching the galaxy for more tardigrades), Burnham realizes the creature is being harmed -- well, slowly killed -- by its use. She, Stamets, Culber and Cadet Tilly begin the search for a workaround, involving injecting a willing human with tardigrade DNA, effectively transforming him or her into a spore navigation computer. But such an experiment is outlawed by the Federation, and Discovery needs jump capability immediately to attempt a rescue of Lorca from Klingon space.

That leaves two options: potentially kill the tardigrade, or violate the law (and acting Captain Saru's orders) and inject a human. Stamets chooses the latter, saving the day, but at what cost? Not the ethical or even legal cost, but to himself? He awakens with a beatific smile on the floor of the reaction cube in engineering, having not only gotten the drive -- his life's work -- to function, but to have communed with spores. For an astromycologist, it doesn't get much better than that.

But how might all of that connect to Star Trek's mirror universe? We can only theorize, because 1.) this whole thing hinges on instantaneous space travel via spores, and 2.) it's science fiction, but it's possible that Stemets' link to the Mycelial network not only allowed him to navigate Discovery to a far-flung location, but also brought him in contact with a parallel universe. It's definitely a working theory, but if Enterprise's "In a Mirror, Darkly" can deposit the USS Defiant lost in a "dimensional fracture" in the TOS episode "The Tholian Web" into the past of the mirror universe, then why can't Stemets' -- and Discovery's -- cosmic journey trace a similar path, crossing from Star Trek's Prime Universe into the mirror universe? No wormholes, equipment malfunctions or multidimensional transporter devices required.

Star Trek: Discovery's explanation of the events will undoubtedly be every bit as interesting as their ramifications. We know Starfleet ultimately doesn't adopt the displacement-activated spore hub drive, despite its early successes in the war against the Klingon Empire -- otherwise, it would be standard technology on Enterprise, Voyager and every other subsequent vessel introduced in the franchise. Is it possible the decision to abandon the technology has little to do with the tragedy on the USS Glenn (well, obviously not), the ethics of harming tardigrades or injecting their DNA into humans, and everything to do with the risks of collapsing interdimensional barriers?

Whatever the case, the already-dark Star Trek: Discovery, marked by mutiny, a warmongering captain, and a disturbing final meal, is about to get even darker.

Starring Sonequa Martin-Green as Michael Burnham, Star Trek: Discovery airs Sundays at 8:30 p.m. ET/PT in the United States on CBS All Access, in Canada on Space and in most other countries on Netflix.