As the boundaries between worlds begin to dissolve, Lyra and her daemon help Will Parry in his search for his father and for a powerful, magical knife.

Lyra and Pantalaimon (now a pine-marten) are back at Oxford. But, their peace is shattered by Ragi, the daemon of the witch Yelena, who is searching for a healing elixir to cure his witch.

"The world-changing events of The Amber Spyglass are behind them, and Lyra and Pan find themselves utterly changed as well. In Serpentine, they journey to the far North once more, hoping to ask the Consul of Witches a most urgent question. This brand-new story, a beguiling must-read for Pullman fans old and new, is a perfect companion to His Dark Materials and a fascinating bridge to The Book of Dust."--Dust jacket.