The Brontë sisters' first poetry collection has just been published, potentially marking an end to their careers as amateur detectors, when Anne receives a letter from her former pupil Lydia Robinson.

Lydia has eloped with a young actor, Harry Roxby, and following her disinheritance, the couple been living in poverty in London. Harry has become embroiled with a criminal gang and is in terrible danger after allegedly losing something very valuable that he was meant to deliver to their leader. The desperate and heavily pregnant Lydia has a week to return what her husband supposedly stole, or he will be killed. She knows there are few people who she can turn to in this time of need, but the sisters agree to help Lydia, beginning a race against time to save Harry's life.

In doing so, our intrepid sisters come face to face with a terrifying adversary whom even the toughest of the slum-dwellers are afraid of . . . The Red Monarch.