This episode is apparently a bit of a temporary swerve from the main storyline. Specifically, we're finding out what's going on with Emperor Philippa Georgiou and what will happen to her. In the real world, the writers have to get Michelle Yeoh's character back from the future so she can helm the Section 31 series. (As far as I know, that's still on--I haven't heard anything about it being canceled.) Now, whether she will return to the main timeline, given the events of this episode, is still up in the air, I think. Presuming this doesn't turn out to be some Q-inspired "this is your life, Philippa" fever dream. We'll see.
Georgiou's story takes up most of the episode, but there are various degrees of movement in a couple of other storylines. After many attempts, Adira reboots the algorithm that decodes the signal emanating from the nebula. They haven't slept and are stressed, not only because of the responsibility thrust upon them and trying to cope with integrating their previous Trill hosts, but because their lover Gray has withdrawn from them. Stamets gently points out that perhaps Gray has a reason for doing that--didn't he want Adira to make friends, after all? Adira objects: "He doesn't have the right to decide that for me." "No," Stamets says, acknowledging their point. "He doesn't."
The signal Adira unscrambles turns out to be a Kelpien ship, the science vessel Khi'eth. (So much for the theory that it was the Discovery itself, as shown in the Short Trek "Calypso.") It was sent a few years before the Burn, a century ago, and has been broadcasting on a loop ever since (although Adira points out that the final moments of the transmission--probably crucial moments--could not be decoded). The Khi'eth was sent in search of something called a "dilithium nursery" when they were trapped inside the nebula. Saru, unsurprisingly, is fascinated by this, watching the transmission over and over after Adira and Stamets are dismissed.
In another short scene, Book talks with Saru as the captain walks down the hallway, saying that he intends to stay around and can be of use. He offers up some intel--the Emerald Chain are conducting "training exercises" that are anything but--that Saru has already heard from Starfleet sources. Saru doesn't quite accept Book's offer, telling him he has to adhere to protocols for this sort of thing and inviting Book to read the Federation manual, but he doesn't quite turn it down, either. He says that when he and Discovery first arrived in the future, they were eager to help and had to wait their turn. He tells Book he has to "wait for his moment."
But the main storyline belongs to Philippa Georgiou and Michelle Yeoh. The episode opens with Culber and David Cronenberg's character, Kovich, examining the results of her scans. (And may I say this is one of the odder guest roles this show has had? Although Cronenberg doesn't do too badly with it.) Bluntly, Georgiou's problem is that she is both a time traveler and originated in the Mirror Universe. Apparently you can do one or the other, but not both. Discovery's crew jumped forward 930 years, but they're still in their own universe. Georgiou's molecules are trying to return to her universe and time, and are slowly tearing her apart. There is only one recorded instance of this happening before, a poor fellow named Yor, and his torment became so acute he petitioned the Federation for euthanasia. (And they couldn't return him to his universe and time because "the Temporal Accords are ironclad"? Really? Even when someone is dying? That doesn't sound very compassionate, ethical or Trekkian to me.) Kovich counsels Culber not to tell Georgiou what is going on, because as a Terran she will seek a glorious death in battle, and "do you want that loose on your ship?" He says it would be best to sedate her and confine her to the brig until she dies. Culber doesn't accept this, and asks the newly combined ship's computer/Sphere data: "Is there another solution?" It answers seconds later: "There is."
(I have mixed feelings about this. I really hope this new sentient Sphere-comp doesn't become some sort of hand-wavy magic eight ball that will provide an answer to every problem. It could, very easily, as it holds some 100,000 years of galactic history and records of countless sapient species. As far as that goes, why isn't there a gaggle of Federation scientists on board Discovery studying this marvel?)
Culber, Michael and Saru take the results of the Sphere data to Admiral Vance: the solution can be found on the planet Dannus V, an uninhabited world close to the galactic rim and far away from where the Emerald Chain is conducting their "training exercises." Saru starts to object, saying Discovery must remain to keep an eye on the Chain, but Vance, surprisingly, says he'll authorize it--after he asks Michael if she'll be able to let Georgiou go if things go bad. Michael replies that she will. After the others leave, Vance talks to Saru, explaining his reasoning: "A crewmember is drowning. If we let her drown, your crew will never look at you or the Federation the same way again." He has a point, certainly...but on the other hand, Georgiou isn't a crewmember. She was just yanked willy-nilly into this universe because of Michael Burnham's guilt over the death of Prime Georgiou. And as much as I love Michelle Yeoh, the fact remains that her character is a genocidal tyrant--except, as we'll see, maybe not so much anymore.
Georgiou is sitting in the mess hall trying to eat, and we see one creepy aspect of her condition. Her hand is phasing out of this reality, to the point where she can't even grasp her wineglass--her fingers keep passing through it. Tilly, seeing this, sits at the table and offers to help her with everyday tasks. Georgiou, made nastier than usual by her condition, insists there is nothing wrong with her hand, and to prove it, she upends Tilly's plate of food all over her front. She tells Tilly that they should take a phaser and "put her down like a dog." Michael interrupts and tells Georgiou there's been a development and Culber wants to see her.
We don't see this conversation, but afterwards we drop in on Georgiou in one of the ship's gyms, thumping the hell out of a punching bag. Her simmering rage at her situation boils over, and she tries to goad Michael into fighting her. There is an interesting juxtaposition in this scene, Georgiou talking about the dynamics of her relationship with Prime Michael, as opposed to her relationship with Mirror Michael, that is part of the callbacks to the Mirror Universe (along with Georgiou referring to Sylvia Tilly as "Killy," her name in the MU, which are setups for what's going to be going down here). I guess those could be seen as a bit heavy-handed, but it's a reminder that there's a lot of water under the bridge and loose ends between Georgiou and both Michaels.
Discovery jumps to Dannus V, and Saru and Tilly come to see Georgiou and Michael off. Saru admits that he has learned as much from the Emperor as he did Captain Georgiou, and the two of them shake hands. It's evident that even though she doesn't want to admit it, Georgiou respects Saru. Tilly, on the other hand, after saying that "weirdly, you've been good for me," hugs the Emperor, much to Georgiou's utter confusion. Then she and Michael beam down to the planet, emerging in a bleak landscape covered with snow.
Georgiou and Michael continue their prickly discussion/argument as they tread through the snow, with the Emperor pointing out (rightly) that Michael still feels guilty about Georgiou Prime. They reach the coordinates given them by the Sphere data, and there's no one there--until they turn around and there's a door standing there in the snow, and a guy in a suit and a bowler hat, chomping on a cigar, sitting at a table and reading a newspaper.
There's been a lot of speculation that this is one of the Q Continuum, so much that everyone seems to be calling him Qarl, even though he says his name is Carl. (To be fair, I imagine the Q would find the Emperor even more interesting than Jean-Luc Picard.) At any rate, he dances around who/what he is and what he's doing there, tells Georgiou the door is a "cure for all your ills," and points out the paper he's reading shows Georgiou's death the next day and says she's wasting time. Georgiou finally decides the door is a chance, and she's going to take it. She walks through--
--and ends up in the Mirror Universe, back as the Emperor, on the very day Michael and Gabriel Lorca betray her.
The rest of the episode is a reimagining of what happens that day. We probably won't find out until Part 2 if this is a retcon of the show's Season 1 storyline, which is what it would end up being if the events hold (although I certainly wouldn't mind seeing Jason Isaacs again). What's most interesting about this is that we're shown that Georgiou's time on board the Prime version of Discovery, and her relationship with Prime Michael, as much as she has resisted it, has changed her. When discussing Michael's plot with Killy, she proclaims that "it's not too late for Michael to make a different choice,"; she tells Michael at their final confrontation, "Do not confuse growth with weakness," and asks why Michael didn't come to her, saying she could have always done so; and most importantly, she treats slave-Saru as a person rather than how she looked at him before, which was, ickily, food. I'm sure this is intended to serve as an introduction to the new Georgiou who will be starring in the Section 31 show--we really can't have the previous cartoonishly evil sociopathic Emperor as our protagonist, after all. And at least in this episode, they take care not to soften her too much, since Michelle Yeoh is so good at showing us "bad" Georgiou. But I think if they keep her in this vein, some fascinating layers and contradictions are added to the character, and Yeoh portrays them very well.
At the end, after she foils mirror-Stamets' attempt to stab her (after he puts on a little play, complete with Cirque de Soleil-style acrobatics, recounting how she rose to her position--I wonder who wrote those lyrics), she follows Michael down the hallway and confronts her about Michael and Lorca's betrayal. We finally find out why Mirror Michael hates the Emperor so; she was "picked off the trash heap," where she was somebody, and brought into Georgiou's household, where, as far as she is concerned, she is nobody. In other words, Michael wanted to rule her nasty little hell rather than live in Georgiou's heaven. Michael spits, "Execute me, Mother," and Georgiou takes up the sword to do so--but pulls her strike at the last second, saying she knows how this story ends, and she's not going to go though it again. She tells Killy to take Michael to the agonizer.
Now we have to find out if this is really happening in Discovery's past, if this is an alternate timeline, or if it's all a product of Q's interference and Georgiou's dying brain. I imagine a lot of people will find this a distraction from the main storyline, and I'm still not sure it needed to take up two episodes. The final judgment on that will come with Part 2.