
The Subtle Knife
The second book in the "Dark Materials" trilogy, published in 1997.
Will is 12 years old and he's just killed a man. Determined to discover the truth about his father's disappearance, he steps through a window into another world. There, he meets a girl called Lyra who, like himself, is on a mission.
The two then embark on a journey that takes them through many strange and sometimes terrifyingly different worlds, encountering all kinds of creatures from ghosts to myserious "spectors"..