We return to Victorian England this week, amidst an odd plague of waxy red corpses. Bodies are turning up in the river, one of which died with an image of the Doctor seared into his eyes. The brother of this unfortunate man turns to Madame Vastra for her investigative help. Their search leads them to a place called Sweetville, which is a factory town being built by Mr. Sweet and Mrs. Gillyflower. Gillyflower is the face of the operation, sermonizing to the masses about the horrors of modern life. She uses her daughter Ada as an example, railing about how the young woman was blinded by her own drunken father.
Young men and women flock to live and work in Sweetville, but only the prettiest and brightest are accepted. Jenny is sent in as a plant, and she quickly discovers that those who are taken into Sweetville are never heard from again. While she snoops around the factory, she learns it's not a factory at all – or at least, not the match factory it's claiming to be. Instead, it's pickling its young residents in a vat of red goo, preserving them for some post-apocalyptic scenario. It's here that Jenny finds the Doctor, chained up and partially paralyzed from the red goo, having been saved from the river by Ada. Once he's gotten the red goo washed off, he reveals through a series of flashbacks how he and Clara came to be Gillyflower's victims. The preservation process didn't work on the Doctor, but it worked on Clara, who's been stashed in a giant jar, like a survivalist's stash of dried fruit. We also learn how the Doctor came to be the last person the dead man saw, when the poor fellow stumbled into the Doctor's cell looking for help before shuffling off this mortal coil.
Vastra recognizes the red goo as the venom of a leech from 65 million years ago. In dilute form, it's being used to preserve Gillyflower's chosen few. Unfortunately, she plans on unleashing it on an unsuspecting world where, somehow, it will kill rather than preserve the population. It's all very... hand-wavy. With Ada's help, the Doctor and friends rescue Clara and confront Gillyflower. Only now do we meet the elusive Mr. Sweet, who is actually the lobster-like leech of yore, currently living under Gillyflower's bodice. After Ada learns that it was actually her mother who blinded her during experiments with the venom, she provides the crucial assist to defeat her.
All seems well until Clara returns home to the Maitland house, where her young charges are waiting for her. They've found pictures of her from the haunted house and the Russian sub, and have concluded that she's a time-traveler. They've also found a picture of Clara the nanny from Victorian London, and Clara's like, "No, I was in Victorian Yorkshire!" Busted! So she not only learns that there's been another version of herself, but inadvertently reveals the truth to the kids. They promise to keep silent on the subject, so long as she takes them on her next adventure. Stay tuned for the full weecap.
For a moment, it's almost like we've stumbled back into a time when Fringe was still on, because some big, white, superimposed lettering on a building tells us where we are. In this case, it's Yorkshire in 1893. The skies are sooty and the streets are muddy. "If I've not returned in an hour, you must fetch the police," says a man's voice. We've moved inside one of the buildings now. "Oh, Edmund," a young blond woman sighs to the speaker. They hug and kiss and he assures her that all will be well. "But we must get to the bottom of this dark and queer business no matter what the cost," he says. With that, he disappears behind a door from which a throbbing red light emanates. A moment later, the woman is confronted by a pack of sternly dressed young woman being led by Dame Diana Rigg. "Mrs. Gillyflower!" the blond says. "We have come about your husband," Mrs. Gillyflower says. "Such a tragedy." Mrs. Gillyflower offers her condolences on her late husband, who's meeting his demise somewhere beyond at red, glowing door. He screams in agony. "We're so sorry for your loss," says Mrs. Gillyflower.
When Edmund's brother goes to see him at the mortuary, he finds that the corpse is bright red. Edmund's mouth is still open in a silent scream. "That's not the first one in here looking like that," says the - well, no title is given to him, so let's call him the attendant. "The Crimson Horror, that's what they're callin' it," he says with some delight. Edmund's brother seems as queasy at the man's manners as he is at the sight of the corpse.
He seeks out the help of Madame Vastra and Jenny, having heard of their penchant for investigating strange cases. The brother explains that Edmund and a young woman were working undercover for a news story. He shows Vastra photographs he's taken of his brother's eyes. At first she's dismissive of the idea of an optigram that can show an imprint of the last thing dead Edmund saw. But then, pulling back her veil, she takes a closer look. Seeing Vastra's reptilian appearance for the first time, he faints dead away. Later, Jenny develops the rest of the pictures. "I think, Madame, that we'd better make plans to head north!" Vastra looks at the pictures and sees what Jenny has seen: captured in Edmund's eye, an image of the Doctor. Also, Jenny still calls her wife "Madame"?
In their carriage en route, Vastra exposits that they're headed towards Sweetville. The proprietor is recruiting members. "She's only interested in the fittest, most beautiful," Vastra says. Strax volunteers to go undercover, and is surprised and a bit disgusted that Vastra has chosen Jenny for the job.