Setting
The setting is a world dominated by the Magisterium (commonly called "the Church"), an international theocracy which actively suppresses heresy. In this world, humans' souls naturally exist outside of their bodies in the form of sentient "dæmons" in animal form which accompany, aid, and comfort their humans. An important plot device is the alethiometer, a truth-telling symbol reader. By setting the alethiometer's hands to point to symbols around a dial a skilled practitioner can pose questions, which are answered by the movement of a further hand.
Plot
Twelve-year-old Lyra Belacqua runs wild with her dæmon Pantalaimon around Jordan College, Oxford, under the guardianship of the college's Master. One day, she witnesses the Master poison wine intended for Lord Asriel. She warns Asriel, whom she believes is her uncle, not to drink the wine, then spies on his lecture about "Dust", mysterious elementary particles attracted to adults more than to children. Asriel shows the college scholars images of a parallel universe seen through the Northern Lights amidst a concentration of Dust. The scholars agree to fund his controversial research, which is considered heretical by the oppressive Church.
Lyra's best friend Roger goes missing, presumed kidnapped by child abductors known as the "Gobblers". Mrs Coulter takes Lyra to her home in London, but before Lyra leaves Jordan, the Master entrusts her with an alethiometer, a strange truth-telling device, which she quickly learns to use intuitively. After several weeks, Lyra discovers that Coulter is the head of the Gobblers, or "General Oblation Board", a secret Church-funded project. Horrified, Lyra flees into London and is found by the Gyptians, canal-faring nomads, many of whose children have also been abducted. They reveal to Lyra that Asriel and Coulter are her parents.
The Gyptians form an expedition to the Arctic with Lyra, where they believe the Gobblers are holding their children. They stop in Trollesund, where Lyra meets Iorek Byrnison, the dispossessed royal heir of the panserbjørne (armoured bears). Lyra uses her alethiometer to locate Iorek's missing armour; in return, he and his human aeronaut friend, Lee Scoresby, join her group. She also learns that Lord Asriel has been exiled, guarded by the panserbjørne on Svalbard. Trollesund's witch consul tells the Gyptians of a prophecy about Lyra which she must not know, and that the witch clans are choosing sides for an upcoming war.
The search party continues towards Bolvangar, the Gobbler research station. Guided by the alethiometer, Lyra detours at a village and discovers an abandoned child who has been cut from his dæmon and who soon dies. She realises the Gobblers are experimenting on children by severing the bond between human and dæmon, a soul-splitting process called intercision. Lyra and her companions are attacked by bounty hunters, and Lyra is captured and taken to Bolvangar, where she is briefly reunited with Roger before being sent to be separated from Pantalaimon. Just before this can occur, Coulter arrives and halts the intercision process. She tells Lyra that intercision prevents the onset of troubling adult emotions, though it has not yet been perfected.
Lyra activates Bolvangar's emergency alarm, sets the station on fire, and evacuates the children, where they are rescued by Scoresby, Iorek, the Gyptians, and the witch clan of Serafina Pekkala, who battle the station attendants as Lyra, Roger, and Iorek flee in Scoresby's hot air balloon. Lyra directs the witches to tow the balloon towards Asriel in Svalbard, but she falls out and is taken by the panserbjørne to the castle of their usurping king, Iofur Raknison. She tricks Iofur into fighting Iorek, who arrives with Roger to rescue Lyra. Iorek kills Iofur and regains his place as the rightful king.
Lyra, Iorek, and Roger continue onwards to Svalbard, where Asriel has continued his Dust research in exile. He tells Lyra all he knows of Dust: that it has spawned parallel universes, it is somehow connected to death and misery, and that the Church believes it is the physical basis of sin. Lord Asriel travels with Roger through the snow, Lyra and Iorek follow using the tracks of Asriel's sled. Asriel ascends a mountain with Roger as Lyra and Iorek and his squadron of bears battle the witches that are allied with Asriel. Mrs Coulter and the Tartars arrive in a military airship and attack the bears. During the battle, Mrs Coulter follows Lyra to the top of the mountain, where Lord Asriel and Mrs Coulter embrace at the peak of the mountain where Asriel has set up his equipment. Suddenly, Lord Asriel severs Roger from his dæmon, killing Roger but releasing an enormous amount of energy that tears a hole in the Northern Lights into a parallel universe, through which he walks. Devastated, Lyra and Pantalaimon also pass through the opening in the sky.
