13-year-old Lyra lives in a parallel world where every human’s soul exists outside their body in animal form, known as a ‘daemon’. Lyra’s the subject of a world-changing prophecy and has an unexplained ability to interpret the alethiometer, a rare, mystical device able to answer any question. Lyra was raised as an orphan, but learns that she is the product of an illicit affair between her ‘uncle’ Lord Asriel and the villainous Mrs Coulter. Asriel is an explorer whose controversial experiments with Dust – a mysterious, invisible substance that surrounds adults but not children – have made him an enemy of religious rulers The Magisterium, which sees Dust as a manifestation of Original Sin and seeks to eliminate it. Mrs Coulter works for The Magisterium and leads secret, cruel experiments in the Far North that sever children from their daemons in an attempt to rid them of Dust, killing many in the process and leaving the survivors empty husks.
With the help of witches, an aeronaut and an armoured bear, Lyra and water travellers The Gyptians storm Mrs Coulter’s research station and free the surviving children. Lyra helps armoured bear Iorek – an exiled King – regain his throne, and she and Roger go to her father’s mountain laboratory. Lord Asriel kills Roger by cutting away his daemon to create an energy surge to open a window to another world, which Asriel walks through. Mrs Coulter, who reveals a deep love for their daughter and a continuing attraction to Asriel, refuses to follow him, but Lyra passes into the next world to try to stop him and to get revenge for Roger’s death. At the same time, in our world, teenager Will goes through a window used by Mrs Coulter’s villainous lover, Lord Boreal to pass between Lyra’s and Will’s worlds. Will is on the run from Boreal discovers the existence of a magical knife in a tower surrounded by angels and thinks Will is the key to finding it.