At the end of the Northern Lights, Silver-tongued Lyra watched in fear and admiration as her father, Lord Azrael, created a bridge between the worlds. Lyra and her demon, Panteleimon, are now lost in another universe, where they meet Will Perry, a fugitive from the third universe. Wil found a small window between Cittagaze (a place where children roam unhindered, but invisible Ghosts suck the spirit of adults), and his Oxford, which, with its "Royal Burgers" and cars, is frighteningly different from Oxford, who knows Lyra. Will's father, a researcher, disappeared years ago, but recently some suspicious individuals began to ask questions about him, and now, after accidentally killing one of them, Will is wanted by the police. Armed with the Hidden Knife, a tool that cuts any material (including the one that separates universes) and the Lyra Alethiometer, the children set out to find John Perry, with adults of various stripes in desperate pursuit. Lyra's finest qualities, her bravery and quick thinking, are stretched to the limit as she must lie, forge, and steal to be with Will in safety. However, she must also know when to tell the truth and whom to trust, for, although she does not yet know it, she has a huge role to play, in the coming battle between good and evil.