Cassidy Heathborne has a compact, road-lean build that seems to fold into doorframes and unfold somewhere else. Her movements are so economical that observers often realize she has crossed a room only when she is already at its far end. Her jaw is broad at the hinge and narrows to a neat point; when she eats, she cuts food into exact squares and chews with her mouth closed, while her rare laugh shows small, slightly crowded incisors. Within a minute of meeting her, most people notice her thumb checking the flat brass clasp at her collar, even when it is already fastened. She leaves an impression of immaculate control, like a sealed letter someone has already opened.

Cassidy is scrupulously formal about promises and fiercely protective of her independence, yet she will break a contract without hesitation if it endangers bystanders. In professional settings she is composed, precise, and difficult to surprise; among people she trusts, she has a dry, almost mischievous humor. She dislikes being thanked for work she considers a duty, but quietly remembers every kindness.

Cassidy grew up carrying sealed legal notices between magistrates and dockside families in the river city of Bellweather, learning which doors opened for a clean coat and which opened only after midnight. At twenty, she was hired to extract a witness from a burning tenement during a politically arranged purge. Her employer had ordered her to retrieve a document, not save the people inside. Cassidy chose the people, and the delay cost her younger brother, Bram, his right hand when a collapsing stair trapped him. That night changed her from a quick courier into a deliberate professional who insists on knowing what a contract will do to ordinary lives. She trained under an aging infiltrator named Ysabet, then left her service and became self-employed. She still sends money to Bram, now a printmaker who refuses to forgive her for deciding what he needed. Her current trouble is a set of contracts bearing her forged seal, each directing violence toward witnesses she once protected. She suspects her former employer, Magistrate Odran Pell, is baiting her into exposing the names she hid.