Tilda Fenn was born in a fishmarket tenement three streets back from the Ratwharf piers, the middle of five children born to a longshoreman father and a net-mender mother who died of a winter fever when Tilda was nine. Her father, Joss Fenn, worked the Harbor Kin's cargo runs, and Tilda learned to walk on wet planks before she learned to read. By ten she was running sealed parcels between warehouses for the Kin, small enough to move through gaps in the harbor wall that no grown smuggler could use, and by twelve she had picked her first lock with a bent nail and a stolen file. The Kin's older dockworkers called her the Wharf Rat, and the name stuck because she wore it proudly.
Dockmaster Crane caught her fourteen years old and knee-deep in his ledger room, copying shipping manifests by candlelight. Instead of dragging her to the Watch, he made her copy the manifests properly, teaching her to read shipping codes, harbor ciphers and the Kin's private marks in the process. It was the closest thing to an apprenticeship she ever received, and she has robbed him a dozen times since, which both of them consider a form of affection.
At nineteen Tilda broke from the Harbor Kin and started working independent jobs, which the Kin considers an unpaid debt and Mirelle Vantt, who trained her, considers a personal betrayal. Tilda does not talk about why she left, and the truth is in the Kin's ledger: her father died owing a debt for cargo he moved for a rat-masked buyer, cargo Tilda now suspects was the cult's. She read the entry years ago and told no one, and the guilt of it sits in her chest like the sweet stench in the city's air.
When the Weeping Sister drifted into the harbor two weeks ago and the plague began, Tilda's world shrank to the fishmarket tenements where her surviving family, two brothers and a widowed aunt, wait behind a red-crossed door. She has spent the quarantine running food through the checkpoints, bribing guards with stolen silver, and mapping every gap in the harbor wall looking for a way out. She has found routes that work for one small halfling and none that work for a family, and the knowledge that she could leave alone and has not is the heaviest thing she carries.
She carries a brass whistle she picked from the body of an Ash Watch guard who died at the north wall the night a family was killed trying to flee. She was there. She did nothing. She has never told anyone.
Now she has fallen in with Captain Vey's investigation, because the plague that is killing her city and the cult that brought it are the same thing, and the manifest that proves it is hidden in the wooden leg of the only man on the docks she trusts. She is cheerful because the alternative is weeping, nosy because knowledge is the only currency the quarantine cannot devalue, and allergic to authority because every authority in Nostramus has failed the people she loves. She treats a locked door as a personal insult. She intends to pick every one of them before the city dies.