The first season of Star Trek: Discovery is drawing to a close, and after Sunday night's penultimate episode, it's time for us to start assessing the season arc as a whole. In many ways, this season will ultimately be defined by the long detour we took through the Mirror Universe. All the many subplots and character transformations come back to that or function as echoes of it.

For now, let's set aside the question of whether the Mirror Universe episodes were good and focus instead on narrative mechanics. What does the presence of the Mirror Universe do to our story? How does it change the stakes?

Spoilers ahead. If you read further, your eyeballs will boil with plot reveals for every episode that has aired this season. Don't do it unless you are ready.

No limits

The Mirror Universe is one of those tropes that allows the show's writers to do pretty much anything. We've had everything from time travel and resurrection (I mean, yeah, it's a Mirror Georgiou, but basically she's back from the dead) to creepy alternate timelines (Burnham/Lorca—gross), cannibalism (sure, not technically, but c'mon), characters acting completely unlike themselves, fungus heaven, and extremely weird haircuts. It's kind of a mess.

When you've got a plot device that can make almost anything happen, it seems like your story should explode with new and interesting possibilities. But most of the time, and certainly in ST:DISCO, the Mirror Universe has the opposite effect. That's because fascinating stories are built from equal parts structure and free play. Especially when you're in the science fiction or fantasy genres, a big part of the fun is figuring out how the rules of the world work. There's a distinct pleasure in worldbuilding that sets up limits, because that's when our heroes come up against complex challenges.

The rules of a world can be outlandish, of course. You can have a spore drive that blips all over the universe and accesses a "mycelial network" that's packed with macro tardigrades. That's fine. Problems start cropping up when literally every episode invents a new magical thing that the spore drive can do. Yep, it can travel to alternate universes. Yep, it can travel through time. Yep, it can access the spirits of the dead. At a certain point, this stops being amazing and gets, well, boring.

As I watched the last few episodes of ST:DISCO, I realized that I'd stopped caring what happened because there were literally no stakes. People could basically come back from the dead via their Mirror versions or if the ship traveled back in time (I dread the possibility that we'll see this subplot in a future episode). Nobody had to worry about running out of spores, because Stamets could just destroy the ecosystem of a handy moon by injecting fungus colonies into its crust.

Of course, Star Trek has always had its share of magical tech and just-in-time transporter saves. But, generally, the franchise doesn't suddenly do a 180 and turn transporters into time travel devices or make replicators capable of churning out sentient goblin armies. In Voyager, for instance, one of the major technological limitations (other than the speed of the ship) was that the holographic doctor could not leave the medical bay. But over several seasons, this situation changed. First, the Doctor had a longstanding wish to move around freely. Then he got a piece of future tech that allowed him to wander the whole ship.

The fact that this change merited an entire episode of discussion—and was part of a longer character arc for the Doctor—illustrates how limitations lead to creative challenges. How boring would it have been if the Doctor had suddenly said, "Oh, I just discovered that I actually can move around the whole ship"? There would have been no struggle and no chance for us as viewers to develop sympathy for him as he worked toward his goal.

I'm not saying the characters on ST:DISCO don't struggle. But the rules change too fast for us to feel like it takes heroic (or even ordinary) effort to overcome challenges.

All the bad stuff lives over there

The Mirror Universe takes the edge off of moral challenges, too. This becomes more obvious if we compare the first half of this season with the second half.

During the first six episodes, we were asked to sympathize with characters like Burnham, Lorca, Stamets, and Tyler—people who were arguably broken and maybe even evil. Plus, we had to place our hope in the Federation, which wasn't exactly the upstanding institution it becomes later in the Trek timeline. Sure, Discovery didn't feel like comforting old Star Trek, where I could always trust Picard and Sisko to do the right thing. But I like a good redemption arc, and we got to explore Burnham's relatable struggle to find peace in a galaxy hellbent on making war.

Then came the reveal that so many of us had glumly predicted: Lorca is actually from the Mirror Universe. Suddenly, the murky ethical landscape of the Discovery became a simplistic black-and-white. Lorca wasn't morally conflicted; he was just evil. Stamets wasn't going crazy; he was just in touch with the Mirror Universe.

On a macro level, the Mirror Universe also had the effect of letting the Federation off the hook for all its problematic decisions. In the first half of the season, we felt a sting when Discovery's scientists were told to turn their research into weapons. We experienced Burnham's shame over starting a war that was avoidable. Saru had to swallow the Federation's orders to kill his sparkle people friends to improve the fleet's signals intelligence. Sarek, who was shaping Federation policy, nevertheless felt that humans were an inferior race.

My point is that the Federation was doing all kinds of things that would have gotten Picard's knickers in a bunch. Our beloved interspecies institution of exploration began to seem proto-fascist, at least until we saw the so-extreme-it-felt-like-parody fascism of the Mirror Universe's Terran Empire. Once we've seen Burnham eat the brain tentacles of Saru's pals while everybody on the Mirror Shenzhou murders each other to get promotions, the Federation can claim the moral high ground.

Instead of showing us a Federation slowly getting itself together and taking the difficult path toward social democracy, the show gave us the plot equivalent of the logical fallacy that bad things turn good when compared to even worse things. Actually, no, they don't. The Federation isn't suddenly a Really Nice Organization just because the Terran Empire is a giant poopchute.

Now, it's as if every bad thing the Federation does is actually because of Mirror influence. And the super bad thing that the Discovery is about to do—basically mapping the Klingon home world in order to genocide everyone on it—is under the command of Mirror Georgiou. Of COURSE it is. Because when we need to make the Federation good again, we just have to get rid of her and everything will be great. No need to change the Federation's regulatory framework or put some checks and balances in there so Admiral Bloodlust can't freakin' burn an entire planet down after secretly installing a non-Federation interloper as captain.

I'm not saying I want to watch Star Trek: The Galactic Foreign Affairs Committee, but I wouldn't mind a resolution that's more nuanced than "throw the bad guy through the moon door erm I mean mycelial sun blob door or whatever."

The Klingducken reveal

Which brings me to Tyler's story arc. He's the dude whose personal struggle is like a mirror (heh) of the struggle between Federation and Terran Empire. He's a Klingon wrapped in a human wrapped in a Klingon—a Klingducken, as my pal Charlie Jane Anders put it. Also, it turns out that literally everything about him—from his PTSD-inducing rape to his DNA—has all been a misdirect.

So here's what that means. I'm just going to lay it out for you.

1. Tyler's horrifying rape trauma, which informed the plot of several episodes and led to many ultra-disturbing scenes of sexual violence and gratuitous Klingon nipples, is not actually a rape. In fact, it was just Voq and L'Rell making love.

2. There is such a thing as a "species reassignment protocol" where you can suck out a person's entire consciousness and genetic identity and squirt it into another person. Also, you can use glowing finger wires to turn the resulting person into either A) the person they were, or B) the person who was squirted into them.

3. The result is not actually a "reassignment" but a hybrid (maybe?). He wants to be treated like the human Tyler but calls himself Klingon during a seriously WTF argument with his ex, Burnham, whom he tried to murder.

4. The intense and relatively realistic way ST:DISCO handled PTSD has now been thrown into the trashcan along with literally every piece of character development for Tyler.

Taken together, these four points add up to bad storytelling. (Also—and I know it's not Star Trek's job to help people suffering from PTSD—but I can't help feeling that it's incredibly disrespectful to write a plot reveal where PTSD can be cured with finger wires and isn't even based on real trauma in the first place.)

Just as the Mirror Universe allowed us to whoosh away the moral ambiguity of the Federation, the Klingducken reveal lets us dismiss Tyler's internal conflicts. It's as if Star Trek: Discovery asked a bunch of really difficult questions about identity and democracy and then answered them by handing us a hot chicken sandwich. I love hot chicken, but you can't resolve this kind of story with it. "I made a lot of bad emotional choices," Burnham tells Sarek as this week's episode comes to a close. In the second half of the season, this show makes a lot of bad narrative choices, too.

We can return to this issue next week, after the final episode has aired, and explore whether the season finale makes me completely wrong. I fear, however, that I am not.