Serpentine by Philip Pullman follows Lyra Silvertongue and her dæmon Pantalaimon a few years after the events of His Dark Materials. They travel to Trollesund to visit an old contact and try to understand a strange phenomenon: they can sometimes separate physically, which should not normally be possible for humans and their dæmons.
During their visit, they learn from a witch-consul that witches can naturally separate from their dæmons. This helps them reflect on what is happening to them and on the changing nature of their bond.
The story focuses mainly on their emotional relationship, showing tension, vulnerability, and the difficulties they face after past trauma.
In the end, Lyra and Pan come to understand that their connection is still strong, but it requires trust and honesty as they grow and change.