Madeleine Barquist, police veterinarian and daughter of Jack the Ripper, is dragged by her detectivist partner Astraia Holmes into solving the death of popular suffragist leader Lady Deborah Peacham, killed by a hatpin plunged into her heart during an assault on Parliament. While investigating Lady Deborah's mysterious death, the detectivists become aware of a more vicious murderer lurking in the shadows of society, their series of crimes hidden and unnoticed.

Almost immediately, the world-famous leaders of London's temperance and suffrage communities realize they have secrets to hide and reputations to protect. They grow nervous, threatened by the direction of Maddie's and Astraia's investigation, and soon learn that a hatpin is not the only weapon available to desperate and lethal Victorians.