The Sage Archivist has given herself over entirely to the study of the First City. It began as an academic interest and became something that has consumed everything else: relationships severed, experiments growing strange and unsettling, all of it in the service of understanding something buried beneath London that most people prefer not to think about. Her former partner is frightened for her and has asked for help. Descend into the ruins beneath the city, trace the obsession to its source, and follow the thread of a story about love, memory, and a duty that outlasted the person who first felt it.