Lost in a new world, Lyra finds Will-a boy on the run, a murderer-a worthy and welcome ally. For this is a world where soul-eating Specters stalk the streets and witches share the skies with troops of angels.

Each is searching-Lyra for the meaning of Dark Matter, Will for his missing father-but what they find instead is a deadly secret, a knife of untold power. And neither Lyra nor Will suspects how tightly their lives, their loves, their destinies are bound together...until they are split apart.