The Subtle Knife - Philip Pullman (Dark Materials: 2)

Will has just killed a man.

Frightened and with nowhere safe to turn, he runs.

His escape will take him far beyond his own world, to the eerie disquiet of the deserted city of Cittàgaze, and to a girl, Lyra Belacqua, who comes from a world that runs in parallel to his own.

As they learn to trust each other, Will and Lyra’s fates become intertwined and their safety dependent upon each other’s skill and bravery. For somewhere in the city is the most powerful weapon in all creation, a knife to cut through worlds. A knife that responds only to the hand intended to wield it.