In Will's world, he visits his mother while Lyra heads to Oxford where she encounters Charles Latrom (Lord Boreal). The alethiometer guides Lyra to Mary Malone, an Oxford physicist researching Dark Matter (Dust). Lyra shows Mary the alethiometer, and Mary demonstrates her research that similarly allows computer communication with Dust. Cardinal Sturrock dies, leaving Father MacPhail a possible successor. Dr Lanselius, the witches' peace envoy, testifies that Ruta Skati's attack was a lone act. He is then falsely convicted of spying, heresy, and treason. Will meets his paternal grandparents who want his father's letters. Will leaves as they are calling to report him to police. Mary connects Lyra to her computer. The particles form screen images that Lyra interprets. Lyra tells Will the alethiometer told her to help him. Mrs Coulter urges MacPhail to take a bold action to increase his chances of being elected Cardinal. MacPhail then bombs the witches' territories. Thorold, Asriel's jailed assistant, tells Mrs Coulter that Asriel had intended to sacrifice Lyra to open up the other world, but instead used Roger. When MacPhail is chosen Cardinal, Mrs Coulter threatens blackmail to ensure his continued cooperation.
Tropes in this episode include:
- Adaptational Nationality: Mary Malone was English in the books (although Malone is a surname of Irish origin), but is played by Irish actress Simone Kirby, who uses her own natural accent.
- Composite Character: MacPhail takes on Father Gomez's habit of self-punishment as penance for sins (although his is not pre-emptive).
- Killed Offscreen: Dialogue indicates the cardinal died from his injuries (and quite probably with assistance from Marisa) between the last episode and this one.
- Platonic Cave: Invoked. Dr. Malone's nickname for the machine she designed to communicate with Shadow Particles (Dust) is "The Cave". The reference goes completely over Lyra's head.
- Rank Up: Father MacPhail succeeds in his campaign to become Cardinal.
- Self-Harm: Newly made Cardinal MacPhail does penance for ordering the genocide against the witches by burning the palm of his hands with a candle flame.
- Strange Minds Think Alike: The "Cave", Dr. Malone's laboratory, has a very similar design to Cardinal MacPhail's Magisterium courters. The implication is that Dr. Malone subconsciously based the Cave on the convent cells from her time as a nun.
- Taking the Veil: Inverted. Lyra discovers that Dr. Malone used to be a nun before leaving the church to pursue Physics.
