"The Subtle Knife" is the second book in Philip Pullman's "His Dark Materials" trilogy. It follows the journey of Lyra Belacqua, who is searching for her friend, Will Parry, a boy from our world. Will possesses a unique ability to cut through the boundaries of different universes using a magical knife. Their friendship develops as they encounter numerous challenges and dark forces that seek to control the multiverse.
The novel explores themes of fate, free will, and the nature of consciousness. As Lyra and Will navigate various worlds, they come across a range of characters, including the enigmatic figure of the Specters, who consume the souls of adults. The story delves deeper into the complexities of human relationships and the moral dilemmas faced by the protagonists.