Dr. Sella Marr has a long, spare frame and the compact, economical movements of someone used to working in narrow rooms around beds. She walks with a brisk, slightly sideways glide, turning her left shoulder through doorways first and stopping so abruptly that people sometimes nearly bump into her. Her dark hair is cut unevenly at the nape, as if trimmed with her own shears between emergencies. Her coat is too broad at the shoulders and patched in three different fabrics, but its cuffs are scrubbed almost unnaturally clean. One unexpected detail for a hard-pressed clinic physician: she wears a tiny enamel beetle pin, carefully polished, on the inside of her collar where patients can see it when she leans over them. Her presence suggests a door held shut against a storm, and a person who will not move until everyone inside is safe.

Dr. Sella Marr is attentive and brisk with the frightened, but can be coldly procedural with people who hold power. She is compassionate enough to break rules for a patient and stubborn enough to resent anyone who asks her to account for the risks. In a quiet moment she is wry, almost playful; under pressure she narrows her attention to the next preventable death and may forget every larger consequence.

Dr. Sella Marr grew up above a cooper's shop near the lower ward's public well, where she learned to recognize sickness by smell before she could read a physician's notes. She trained under Iven Galt, a precise but unsentimental doctor who taught her that a clean bandage is useless if the patient has nowhere safe to sleep. During the fever winter, the city closed its gates and the prison began taking blood and marrow from inmates under a so-called voluntary donation scheme. Dr. Sella Marr discovered that prisoners who refused were threatened with lost meals and solitary confinement. She confronted the prison physician, who told her that the clinic's medicine allotment depended on keeping the arrangement quiet. When a child with a blood fever was turned away for lack of supplies, she broke into a locked store room and stole the medicines that saved him. That act cost her license for a year and changed her from a rule-following doctor into a keeper of people first and records second. Now she runs the cramped Thistle Bend Clinic with help from Tegan Urr, a practical apothecary who questions her risks, and receives supplies through a discreet arrangement with prison quartermaster Kett Ordan. Dr. Sella Marr authorized the diversion of several casks of medicinal spirits and antiseptic from a prison shipment to keep the clinic stocked. The casks have vanished, patients are still relying on the diverted stock, and investigators are closing in. She is trying to expose the coercive donation scheme without letting the clinic be shut down or the prisoners punished for speaking.