Last week's His Dark Materials picked up steam with the addition of Will Parry and a second storyline on our Earth. This week, Will is mostly benched. Despite Boreal's orders to search the house, his minions are perfectly happy to sit outside watching, unnerving Elaine and her kid, rather than go full-scale break-in. It allowed the show to bring the main plot up to the same level, with an episode where Lyra is confronted by adults who lie better than she does.
Not that Lyra isn't a good liar. Upon being processed into Bolvangar, "Lizzie" is moved to the top of the list of children to be cut, since she's practically weeks away from hitting puberty. Not that she's first up, that honor goes to Bridget, a girl in giant glasses with who Lizzie was trying to make friends/start the revolution. But Dr. Cooper and company are all nerves right now, between the malfunctioning fire alarm and the imminent arrival of Mrs. Coulter. The latter is assumed to be coming after the escape of Billy Costa. (Apparently, he was not let go, he wandered off.) But viewers know she's really on her way in hopes of finding Lyra.
The fire alarm is a useful distraction, it gives Lyra and Roger a chance to communicate, and a well-timed snowball fight allows them to sneak off and investigate. If Billy Costa's daemon-less zombie wasn't enough to drive home the horror, being confronted with cages of cut-off daemons, and a roomful of zombie children with shaved heads and slow reactions (including Bridget and her huge glasses) lands with a visceral force. Lyra and Roger vow to get out before it's their turn.
The heightened tension helps explain why Dr. Rendal (Amit Shah) jumps a foot and a half when Lyra asks if he's measuring her for Dust. Recognizing she's given too much away, she backtracks airily telling him she washes plenty, there's no dust on her. But her indiscretion does do her a favor when Coulter finally turns up, and she gets called up to have her daemon cut off in front of the boss to show how well things are going. By then, the rest of the kids know who Lyra is, and are in on her planned revolution, even though no one is clear exactly how it's supposed to work.
The Gyptian ragtag army is on their way, despite the kids not believing anyone is coming to rescue them (or could effectively do so upon arrival.) So Lyra's not lying. Nor is she lying when, in desperation, she starts screaming she's Coulter's daughter, and crying out for her mother at the top of her lungs. Rendal's hesitation is enough, Lyra and Pan aren't entirely cut off when Coutler walks in and demands Cooper explain all this ruckus... until she hears Lyra loud and clear: "MOTHER, HELP."
So much for Cooper's demonstration. Lyra is pulled out along with Pan, and taken to Coulter's room, where she demands her mother explain what is going on, in a scene that brings this show, this story, and the last five hours into sharp focus for the first time. Ruth Wilson's performance here is all the magnetism the series needs, as Coulter explains: "Dust is not a good thing. Grownups are infected so deeply it's too late for them, condemned to a life of sin, guilt, and regret. This is for a better future, a better life."
Your daemons are wonderful friends and companions to you when you're young. But at the age that we call puberty, an age you're coming to very soon darling, daemons bring all sorts of... troublesome thoughts and feelings. And that's what lets Dust in.
Lyra isn't buying it. If the experiment was so good, she should have let them cut off Pan from her then, and be glad to do it. Coulter then starts equivocating, how the machine isn't ready, they're still in the experimental stage, it's not safe yet. It's okay for others, those children from the lower classes no one cares about, but Lyra is above them. Their sacrifice, the few for the good of the many, is how discoveries in the name of experimental theology get made.
It's a big ball of classist and racist nonsense, the lies adults tell themselves that results in children in cages here in our world, that lets doctors tell themselves their human experiments on living people are a necessary evil. One day, history will vindicate the atrocities they commit in the name of "the greater good."
Coulter's speech ends with an insistence that Lyra give her the alethiometer, as a symbol of choosing Coulter's side and safety from these atrocities that her class status would afford. Lyra seems to acquiesce; after all, Coulter saved her life, and is promising protection. But the welded shut tin she hands over is no alethiometer, though it speaks volumes that Coulter has no idea it's far too small, as she frantically hacks away at the welds trying to get at whatever's inside. (For all that she pretends to weld so much power, the Magisterium has never let her even see one.) It turns out it's that SpyFly the Gyptians captured back in Episode 3, which angrily flies directly into Coulter's face and attacks upon being released.
Lyra flies out of the room, trapping Coulter and her monkey inside, and sounds the fire alarm. Her timing is perfect - the Gyptians have landed, via Scoresby's balloon, directly into the middle of the compound, and a firefight has broken out. Roger collects the cut kids and their daemons while the Gyptian army collects the other children, and Ma Costa gets revenge for Billy by snapping Rendal's neck. (Best answer to "I was only following orders" ever.) Before the fight can take any Gyptian lives, Seraphina flies in and takes out every last scientist in the compound — save Coulter, who has been delayed from the battle by her duct crawl to get out of the room Lyra trapped her in.
The hour ends with Scoresby taking Iorek, Lyra, and Roger off to Svalbard to free her father from Iofur Raknison. The rest of the Gyptians pack up the children, including the cut ones and their daemons, back to the U.K. in hopes of reuniting them with their families. But things aren't going to be that easy for anyone, as Scoresby's balloon is attacked by cliff ghasts, and Lyra falls out of the basket.