Editing His Dark Materials (section)

===''The Subtle Knife''===
{{Main|The Subtle Knife}}

Lyra journeys through Asriel's opening between worlds to [[Cittàgazze]], a city whose denizens discovered a way to travel between worlds. Cittàgazze's reckless use of the technology has released [[Spectre (His Dark Materials)|Spectre]]s which destroy adult souls but to which children are immune, rendering the world empty of adults. Here Lyra meets and befriends [[Will Parry (His Dark Materials)|Will Parry]], a twelve-year-old boy from our world's Oxford. Will, who recently killed a man to protect his ailing mother, has stumbled into Cittàgazze in an effort to locate his long-lost father. Venturing into Will's (our) world, Lyra meets Dr. Mary Malone, a physicist who is researching dark matter, which is analogous to Dust in Lyra's world. Lyra encourages Dr. Malone to attempt to communicate with the particles, and when she does they tell her to travel into the Cittàgazze world. Lyra's alethiometer is stolen by Lord Boreal alias Sir Charles Latrom, an ally of Mrs Coulter who has found a way to Will's Oxford and established a home there.

Will becomes the bearer of the Subtle Knife, a tool forged three hundred years before by Cittàgazze's scientists from the same alloy used to make the guillotine in [[Bolvangar]]. One edge of the knife can divide [[subatomic particles]] and form subtle divisions in space, creating portals between worlds; the other edge easily cuts through any form of matter. Using the knife's portal-creating powers, Will and Lyra are able to retrieve her alethiometer from Latrom's mansion in Will's world.

Meanwhile, in Lyra's world, Lee Scoresby seeks out the Arctic explorer Stanislaus Grumman, who years before entered Lyra's world through a portal in Alaska. Scoresby finds him living as a shaman under the name Jopari and he turns out to be Will's father, John Parry. Parry insists on being taken through the opening into the Cittàgazze world in Scoresby's balloon, since he has foreseen that he should meet the wielder of the Subtle Knife there. In that world, Scoresby dies defending Parry from the forces of the Church, while Parry succeeds in reuniting with his son moments before being murdered by Juta Kamainen, a witch whose love John had once rejected. After his father's death, Will discovers that Lyra has been kidnapped by Mrs Coulter, and he is approached by two angels requesting his aid.